## Welcome!

This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

## Wednesday, November 27, 2013

### How do elk swim? I think he walked over a bridge! His name is "Bruiser."

 The Whidbey Island male elkImage credit: Sasha Castaneda Whidbey News Times here
OK, it's definitely a fluid dynamics problem to figure out how a lone elk can land our elk-less island. Don't get ants in your pants, this is not post about how humans got to Easter Island or about genetic evolution. It's just a story about one lonesome male elk.
I live on an island. There are three ways to get here: (1) drive over a bridge; (2) take a ferry; or (3) swim. It's 100% unlikely that this moose did not ride a ferry to our island, probably not quite so certain that he walked over the bridge.
So, the common assumption in our local media is that he swam. But, if that's true, why didn't he swim back during rutting season? My hypothesis below is that he's actually not a good swimmer, that he didn't get here by swimming, and that he walked here. If that's true or even likely, we should shoo him back over the bridge so that he can not be so lonely! Having worked in Yellowstone National Park for many years, I can attest that (a) bull elk are not happy during mating season, and (b) that they will great distances for you-know-what.
Here's the story: This handsome guy appeared on Whidbey Island in September of 2012, and is the only elk on Whidbey. He is probably a healthy bull in a mainland herd that no longer tolerated him. The common pattern would have been for him to find new land with a few accompanying females and start a new herd. But, here is now, alone on Whidbey. But, one year later during rutting season, he's still here?  According to the Washington Department of Fish and Wildlife, "the animal decided to stay put." But, is that realistic? If Bruiser could get back to the land of bountious females, would he actually "decide" to stay put? Not a chance in my experience with elk.
So, what is going on? A healthy male elk lives about 15 years in the wild, and can weaight up to a half-ton. Like Bruiser in the photo, they can sport great racks (which everyone on Whidbey hopes will NOT become a target of illegal hunting--beware: there' a great island-watch on this guy....) How far would he have to swim?Elk are strong swimmers, aided by hollow hairs that keep them buoyant. During mating season, they "buggle" a mating noise that carries very long distances. You can see videos of them swimming, but if you Google "elk swim distances", there's no world record for an elk swim. They can definitely ford rivers, but is it an "easy swim" from the mainland to Whidbey as the Washington Department of Fish and Wildlife is saying?
At best, this guy started in a herd in Skagit Bay on the mainland as Fish and Wildlife believes, he would have swum 4-5 miles direct from the Skagit tributaries to here. Not likely? At the very best, he'd have wandered up to Deception Pass (by himself, without his mistresses?) to Deception Pass where he had a narrow passage, but harrowing waters. If he got that far, why not walk across the bridge? On those autumnal days when there are few tourists, long dark nights, why would an elk near the bridge not just take a walk? It would certainly explain why he can't find his way home! What if Bruiser's females are just out of reach on the other side?
It's clearly a fluid dynamics problem (Aside: traffic flow is a fluid dynamics problem) to reunite Bruiser with his herd! It's also an environmental problem because the Skagit Valley herd of 1700 elk have been driving Skagit Valley (mainland) farmers crazy over decades eating their crops. Fertile male elk are being culled from the herd by Federal, state, and tribal hunters, and they are authorized to kill 15 at the moment. Maybe Bruiser is a very clever elk.

## Monday, November 25, 2013

### To storm or not on this Thanksgiving?

 The GFS model forecast by the National Weather Servicefor 4:00 p.m. Thursday PSTtaken from Cliff Mass's blog discussed in text
Hmmmmm...who to believe? If you read CNN.com here, you get the impression that Thanksgiving is going to be a mess. In fact, that article is on the front page of CNN.com with titles "Massive storm for Thanksgiving" and "A side of weather with your story." I was feeling smug that I am staying local for Thanksgiving, and so I turned for a local forecast to my favorite northwest meteorologist Cliff Mass's blog, which is particularly funny today and, as usual, educational.
And, what did I find?An essay on the "lack of storminess and ill-weather" in the Thanksgiving prediction! Cliff usually takes on the Seattle Times, but he missed a chance to take on CNN today! If you read the text of the CNN article, you can see that they are talking about yesterday, today and Tuesday mostly, not about Wednesday through Friday, but the headlines are certainly misleading.
The only place on the mainland to see significant precipitation is far NW Washington State and, Cliff says, "not many folks live there and most of those watch Canadian TV. In other words, they don't count!" (The comments posted today reflects that he has a tolerant readership up in that area of Washington!) He really is in good form in this post. High pressure dominates most of the nation, there are no low pressure systems influencing the mainland (there is one noticeable one off the coast of southern California). He also points out that today (Nov. 25th) is the 6th straight day without rain in the Seattle area, when the normal chance of rain at this time of year is 65%. It looks like we could squeek by through Wednesday without rain, with some moving in on Thanksgiving. That would be 8 straight days without rain, and according to him, the chance of that is about 3%.
But there's more to the story. According to the National Weather Service Weather Prediction Center, Wednesday could be messy in the midwest and east coast. Temperatures will be 10-20 degrees below average in the central east coast and upper midwest regions, and a front over the Great Lakes will produce lake effect snow over the Great Lakes through Wednesday (this does bring back memories of Thanksgiving storms where I grew up in Northwester Pennsylvania, where we got the lake effect snow from Lake Erie). A storm developing over the Central gulf coast will move toward this Great Lakes disturbance to produce moderate to heavy rain that will move from the central Gulf Coast into the Appalachians by Tuesday morning. This system of rain will then move east to the Mid-Atlantic on Tuesday and expand into Northern New England by Wednesday morning. Snow will expand into the Lower Great Lakes Tuesday evening and Wednesday. So, in detail, it's complicated and worth reading the various forecasts/news articles carefully.
As, Cliff also pointed out, Thanksgiving and the first day of Chanukah coincide this year, the first time since 1888, and the next time may be 77,000 years from now! Compounded with the fact that Comet Ison will be the closest to the sun and brightest that same day, as Cliff says , "Happy Thanksgivukkah", or maybe better, "Happy IsThanksgivukkah!"

## Sunday, November 10, 2013

### Typhoon Haiyan may have killed 10,000. 3D structure of typhoons; Carnot engine theory

 Boat in debris in Tacloban on November 10 Photo by Aaron Favila/AP from here
Although confirmed estimates of deaths due to Typhoon Haiyan remain around 1200, there are now credible speculations that there may be as many as 10,000 dead in just one village. My condolences to the people of the Philippines, and best wishes that supplies reach you quickly.
According to this Reuters.com article, 70-80% of the structures in the path of the typhoon were destroyed. Most of the deaths appear to have been caused by a debris-laden storm surge that swept away whole villages. The capital of Leyte province, Tacloban, lies in a narrow cove where storm surges can be focused toward the city. The storm surge appears to have surged at least a half mile inland.
 Tacloban location

 November 9, 2013 Super Typhoon Haiyan imaged by NASA Astronaut Karen Nyberg on NASA's ISS.
The country was not unprepared for this event, and it is sobering that so much damage could still occur.  A question not often addressed is: Are there storms simply too strong for even modern engineering to provide safety?  The heartbreaking scenes from this storm are so similar to those of the tsunami damage from the 2011 Tohoku tsunami that it appears the answer may be "yes."  Could people have survived if all buildings had been made of concrete, and made so tall that people could take refuge above the 15' high storm surge reported? Can concrete buildings be designed to withstand 250 kilometer per hour (155 mph) winds?
What determines the intensity of a tropical cyclone? Remember: typhoon, hurricane, cyclone are just different words for the same phenomenon.  Tropical intensity is usually measured by the value of the maximum wind speed.  Here's a table of cyclone wind speeds from The Guardian:
 From TheGuardian.com November 9, 2013
Haiyan, although the strongest cyclone to make landfall is the fourth strongest in terms of measured wind speeds.
Kerry Emanuel, Professor of Atmospheric Science at MIT, specializes in hurricane physics (see several references to his work at ** below). A tropical cyclone is driven principally by heat transfer from the ocean. They generally develop over water whose surface temperature exceeds 26 C. They occur in three main belts generally within 5 degrees latitude. The cyclones then move westward and poleward at speeds on the order of a few meters per second. Cold water kills them as can unfavorable atmospheric winds.
Emanuel is famous for, amongst other things, his analysis of hurricanes as a Carnot heat engine. The Carnot cycle is a basic concept in thermodynamics. A thermodynamic cycle is the set of thermodynamic conditions (such as pressure, temperature, entropy, enthalpy) reached in a system as energy is transferred from warm to cool regions. In the process, some of the energy is converted to mechanical work.
 The Carnot heat engine of Emmanuel Taken from the Physics Today article referenced at **

In the cross-section diagram to the left, the horizontal axis shows distance from the center of a cyclone, and the vertical axis shows altitude. The colors, from deep blue to dark red represent entropy, with the cooler colors indicating lower entropy. Evaporating sea water transfers energy and entropy from sea to air, and this causes air to spiral inward from A to B.  As it moves, the temperature of the air is nearly constant (an isothermal process), its volume increases as it flows toward the low-pressure core of the cyclone, and its entropy increases. The air then rises rapidly upward (in the eyewall) and outward, from B to C, so rapidly that the process can be considered adiabatic and isentropic (note how the path B-C lies within the constant yellow color). Once away from the storm center at C, the air generally mixes with other storms and is lost from the system, but in idealized models, the air radiates in the infrared wavelengths into space, a process Emanuel considers nearly isothermal, and so it loses entropy. The air then sinks again (D-A) and warms through (nearly) adiabatic compression (in the deep blues of constant entropy). This closes the Carnot cycle.
Emanuel then shows that the velocity of the surface winds is proportional to the difference in temperature between the ocean surface and the high-level outflow (conveniently, 100 C in the figure shown) and the thermodynamic disequilibrium between the ocean and atmosphere, E, which is the difference between the enthalpy of air near the surface and of air in contact with the ocean.  Using these concepts, Kerry then showed (in a 2003) paper, that a limit on maximum sustained wind speeds is about 85 m/s or 195 mph. (He did not comment on the possibility of higher winds as shown in the table above.) He also showed that the average cyclone dissipates about 3E12 watts, equal to the total electrical power consumption in the US in 2000, and that an exceptionally large storm can generate an order of magnitude more power.

**K. Emanuel, Tropical Cyclones, Annual Reviews of Earth and Planetary Sciences, 31, 75, 2003.
**K. Emanuel, Divine Wind: The History and Science of Hurricanes, Oxford U. Press, New York, 2005.
**K. Emanuel, Hurricanes: Tempests in a greenhouse, pp. 74-75, Physics Today, August 2006.

## Thursday, November 7, 2013

### How does Super Typhoon Haiyan ("Yolanda") compare with Jupiter's Great Red Spot?

Updated: November 8, 2013

Super Typhoon Haiyan is now being called one of the largest storms ever. For a nice display of images of 13 of the largest storms, see here. Other posts on this blog related to this are: Super Typhoon Usagi in the Philippines just six weeks ago, including a Table of the Categories of hurricane (cyclone) strength; Tropical Storm Phailin and Thailand; and Cyclone Tracy and the Bill and Boyd song "Santa Never Made it to Darwin" (because Cyclone Tracy struck on Christmas Eve and Day, 1974).

Here is a link to Dave Petley's Landslide Blog that has a post today on the landslide potential due to the storm.

End of upate______________________________________
 Super Typhoon Haiyan, November 7, 2013, 21:30 UTC NOAA image
Super Typhoon Haiyan is headed toward the Philippines, due for landfall Friday morning (here's the CNN.com report on it). At the moment its winds of 195 mph with gusts up to 230 mph make it a Category 5 on the hurricane scale [Note: Weather.com put the winds somewhat lower--sustained at 134 mph and gusts to 155 mph]. (For comparison, we had a fairly major wind storm on Whidbey Island a week ago with winds up to 40-60 mph! Took down a lot of tree branches and some trees, caused power outages not only here but on the mainland for 8+ hours. Quite humbling to think of what it's going to be like in the Philippines.) This is the largest storm to date this year; its diameter is about 800 km (500 miles). For comparison with Yolanda, the most intense sustained winds appear to have been in about 190 mph in several typhoons (Typoons Tip, Grace, Vera, Sarah in the Pacific, and Hurricanes Allen and Camille in the Atlantic), so Yolanda is on-course to be close to a record-setter. More than 3800 people have been moved to evacuation centers, most from the central region of the Philippines. As shown on the adjacent map, the typhoon is projected to cross the South China Sea (to the west of the Philippines) and then hit Vietnam and Cambodia. It's speed has been 20-24 mph.
 Path of Super Typhoon Yolanda
The winds and rain from the storm are one thing, but there are other dangers. The island of Bohol in its path was hit by a magnitude 7.1 earthquake just a month ago. 350,000 people were displaced by that quake and are extremely vulnerable. Last December, Super Typhoon Bopha hit the southern Philippines, killing over 1000 people and affecting six million. A quarter million homes were damaged or destroyed. Landslides during storms in the Philippines are a constant danger.
 Jupiter Great Red Spot NASA image In the high resolution version of this image, objects as small as 600 km (~400 miles) can be seen. Thus Super Typhoon Haiyan, with a diameter of 500 miles-- would be a tiny dot just barely visible.
According to the International Business Times, a Philippines government website specifically dedicated to disaster reduction was hacked just as the typhoon approached and, as of yesterday, was still not accessible. The website was supposed to provide Filipinos with real-time information about threats such as cyclones, tsunami, floods, landslides and fires, as well as providing general safety advice on preparation and surviving disasters.
How do our earth storms compare to the Great Red Spot on Jupiter? This storm was first observed by Cassini in the late 1600's, and scientists believe that it is actually older than that. This is an anticyclonic storm (rotates anticlockwise) with a period of about six Earth days (14 Jupiter days). It's 24,000-40,000 km in EW direction, and 12,000-14,000 NS. It is large enough to contain 2-3 Earth's, so even our biggest storms don't compete! Winds around the edge of the spot reach 432 km/hour (268 mph).
See the Figure caption to compare Super Typhoon Haiyan with the Great Red Spot!

## Tuesday, October 29, 2013

### Huge MegaWave off the coast of Portugal: video

 Big wave of October 28, 2013 from Surfertoday.com This wave is at the so-called Nazare North Canyon (Praia do Norte) Portugal

The news has been full of reports about the big storm that battered England and northern Europe the past few days. News is just coming out about surfers catching the big waves generated by the storm. In the photo above, the two men pictured are competitors in the goal of surfing the world's largest wave. In January, less than a  year ago, Garret McNamara (left in photo) surfed what was believed to be the biggest wave to date then, about 100 feet high. He had previously ridden a 78' high wave in 2011. Carlos Burle, right above, may have topped that record with his ride on a 100" high or greater wave on Monday. A video is here, and one with more wave mechanics is here. The official height of this wave hasn't yet been announced, but speculation is that it may be a new world record.
What generates such waves? In my book "The Dynamics of Disaster" published last week by W.W. Norton Press, I have a chapter on ocean waves, and specifically on rogue waves. I'll highlight a few points here: What is a rogue wave? What happens as they approach shore?
Rogue waves are quite ephemeral, and that has made scientific documentation difficult. In 1861, a wave broke glass windows 85 feet above the ground in an English lighthouse--after climbing up a 130-foot high cliff! This would imply that the wave was 215 feet high, but as of now, no wave near this height has been documented by eyewitnesses or with instruments. Rogue waves are generated by storms, and they are a danger to  shipping, fishing, tourism, and oil and gas production on the ocean.
Here's a quoted footnote from my book that defines rogue waves: "To provide a reference for defining rogue waves, oceanographers have introduced the concept of a “significant wave height.” The significant wave height is the average wave height of the one-third highest waves in a time period (typically taken as 10-30 minutes). Surfers might find the following exercise useful--and sobering: ignoring the small stuff, sit on a beach and make a list of the heights of all incoming waves for 10-30 minutes. For example, 1 foot (1’), 2 feet (2’), 3’, 5’, 3’, 4’, etc. Organize this list from biggest to smallest: 5’, 4’, 3’, 3, ’2’, 1.’ Keep the highest one-third of the values, 5’ and 4’. Then, take their average--4.5.’ This is the significant wave height. A rogue wave is defined as one whose height is two or more times the significant wave height--9’ in this example. In fact, rogue waves with a height more than four times the significant wave height have been documented. In this example, that would be an 18’-high wave. Surfers who are comfortable with 2’ or 3’ foot waves, perhaps an occasional 5’ wave, but not with 9’ or 18’ waves need to be aware that such waves can appear at any time. This is apparently what happened when a wall of water collapsed on and killed the experienced big wave surfer, Sion Milosky, at Half Moon Bay, California, in March, 2011. After nearly an hour of relatively small swells (18-20’) for that day, a rogue wave “bomb” rolled him to the bottom, where he was held down not only by this wave, but by a second as well, in what is known as a “two wave hold down” in surfing jargon. He was found too late, 20 minutes later."
 Map showing the likelihood of encountering a rogue wave within any 24-hour period. Courtesy Burkard Baschek
(Sorry, but I'm not doing well at controlling line spacing in Blogger if this looks wierd)

Broad patterns of wind and ocean currents determine the zones of hazardous rogue waves on the ocean (as discussed more broadly in the book). Four factors can operate simultaneously to determine the height of he waves on the open ocean and near-shore: winds from hurricanes and storms that churn up the ocean surface; the interaction of strong waves moving in opposite directions, such as storm waves interacting with strong oceanic currents or strong opposing winds; constructive interference (addition of wave heights) of random waves; and piling up of waves from the deep ocean into shallow depths along the continental shelves. See book for details! And, it's that last effect that makes surfing so exciting!

## Monday, October 21, 2013

### Megafires: The New Norm

 Sydney skyline with smoke. Photo is from cnn.com here. Photographer is Gregg Wood/Getty Images
Fire is raging outside of Sydney, Australia, and today firefighters are saying that the hoped-for rain is not coming. They now fear that the 50+ individual fires will join to form a "megafire." NPR.com did a 5-part series titled "Megafires: The New Normal for the Southwest"last year (August, 2012) and you can link to it here. This summary is taken largely from that article plus some other references. The weather is dry, lightning abounds, and the last winter was very dry providing lots of fuel. The fires have already burned an area the size of Los Angeles.
Fires are a natural part of ecosystems like those in the American Southwest and Australia. For a hundred years, the U.S. Forest Service had a policy of fire suppression that resulted in the accumulation of a large amount of brush. I'm not sure about the Australian fire suppression policies. However, because Australia sees cycles of droughts and floods, large fires have been a prominent part of the ecosystem evolution.
In the Southwest, up until about 20 years ago forests had as many as 50 times the natural density of trees--typically, Ponderosa Pines (the ones whose bark smells like vanilla on a sunny day!). The forests resembled a thicket of giant toothpicks with mops of green hair on top. This was a result of the fire suppression policies. The Forest Service realized the problem that it had created and began to try to thin the trees by letting naturally started fires (e.g., those started by lightning strikes) burn when structures weren't endangered. They also started prescribed burns on days when wind conditions permitted this to be done safely. Such fires clear out the undergrowth.  However, people don't like smoke from such fires, and when the occasional one got out of control, the Forest Service was subjected to law suits and so they burns were cut back.
Firefighters are now being quoted in the press as saying that the megafires are something new, that they've fought big fires before but nothing like these.  According to Thomas Swetnam, a tree ring expert at the University of Arizona, old trees show scars of fires that burned them, but didn't kill them. Back in the 1600's such fires occurred about every 5-10 years--small grass and shrub fires that left the big Ponderosas and Doug firs alive. But then "around 1890-1900 the record stops--the "Smokey Bear effect."What happened? The Civil War had ended, Reconstruction was nearly finished, and the Manifest Destiny doctrine resulted in the westward expansion. Settlers brought livestock that ate the grass, so fires had little fuel. Then the U.S. Forest Service was formed and, as Swetnam says, "its marching orders were 'no fires.'"Expert wisdom was wrong. (You can see a time-laps series over 88 years showing changes in a forest landscape here.)
The result was a Southwest with forests packed with trees, shrubs and grass--fuel. When fires start in forests with these conditions, the immense heat that they generate actually precooks fuel in front of an advancing fire by drying it out.
There are, broadly, three types of fires (this classification comes from the U.S. Forest Service and is specifically for conifer forests, but general enough to apply here): ground or subsurface fires; surface fires; and crown fires. Ground or subsurface fires spread slowly without visible flames. Surface fires can spread with the wind or upslope (so-called "heading surface fires") or into the wind or downslope (so-called "backing surface fires.") Crown fires advance both through the tree tops and through over the surface. The transition from a surface fire to a crown fire is a significant escalation in the fire intensity, particularly because convection increases allowing embers to be spread far away from the initial fire. Three types of fires are shown in the figure below (taken from the USFS report referenced above).

Forest fire fighters have developed various ways to try to anticipate fire conditions. Van Wagner (see the USFS report mentioned above) hypothesized that the type of crown fire to be expected in a conifer forest on any given day depended on three properties of the canopy fuel layer and two basic fire behavior characteristics. The Fire characteristics are the initial surface fire intensity and the rate of fire spread after the onset of crown combustion. The three properties of the canopy are the foliar moisture content, the canopy base height, and the canopy bulk density. The initial surface fire intensity, the foliar moisture content and the canopy base height determine whether or not the fire will ignite the foliage of the conifer, and the canopy bulk density and the rate of fire spread after crown combustion determine whether the fire can be sustained in the canopy.  The initial surface fire intensity and rate of fire spread in turn depend on windspeed, slope steepness, fuel dryness, air temperature, relative humidity and fuel characteristics. Models such as these are put together in various graphs to illustrate fire potential.
 Van Wagner's diagram for fire classification
Wagner's graph is illustrated here. The abbreviations are: Rate of spreading (ROS) and critical rate of spreading (ROScritical) and Surface fire intensity (SFI) and critical surface fire intensity (SFIcritical). The trap shows that if the surface fire intensity is low, then there is no crowning, only surface fire. If the surface fire intensity is high, then crown fires develop. They are either passive (if the ROS is low) or active (if ROS is high).

## Saturday, October 12, 2013

### Tropical Storm Phailin (Phailin means sapphire in Thai)

 Projected route for Phalin from Accuweather.com at this link
Today another superstorm has attacked India from the Bay of Bengal: Tropic Cyclone Phailin has hit northeastern India. Hundreds of thousands are either fleeing or being forcefully evacuated. Winds over 100 mph, and flooding in excess of 8" are expected, along with storm surges of up to 20 feet near the shore where landfall occurred.   Winds were in excess of 125 mph at the point of landfall at Golpalpur. The US Navy's Joint Typhoon Warning Centre predicted that Phallin could produce gusts up to 184 miles per hour.

 Phailin and related geography From The Weather Channe
In 1999, Cyclone Odisha struck and estimates are that up to 15,000 were killed. Up to this date, Odisha was the strongest tropical cyclone ever recorded in the Indian Ocean, and was the deadliest since a cyclone hit Bangladesh in 1991. It was a category 5 storm and followed a category 4 storm in the same general area by only a few weeks. Tens of thousands fled. The storm surge was 26 feet and it traveled up to 20 km inland.Nearly 7,000 square miles of crops and 90 million trees were destroyed. Nearly 1.7 million people were left homeless. Estimates are that up to 45,000 people died, but the official count stood around 10,000. Many people died of starvation and disease after the storm.

Since Odisha, authorities have vowed to reduce deaths and enforce mandatory evacuations. The area encompassed by the cyclone is home to millions of people. Most live in mud and thatch houses. The army is on standby and helicopters and food packages are being prepared for relief operations.

I have discussed hurricanes and cyclones in a number of other posts (see, for example, here; you can search the blog for others), so here are a few new facts (from the Hindustan Times reference given below).

In contrast to naming of hurricanes in the Atlantic, starting in 1979 cyclones in the Northwest Pacific are named in very different ways. By and large, personal names are not used. The majority of names refer to flowers, animals, birds, trees, or even foods, and some are descriptive adjectives. The names are selected by contributing nation, with the selection being from a list of the countries in alphabetical order.

I've been asked whether any good ever comes of disasters, and hopefully, the Indian's response to this one will be an example. In 1999, only tens of thousands were evacuated from this same area. This time it is hundreds of thousands. Let thoughts and prayers for success in their efforts fly across the ocean to those in the path of Phailin.

Accuweather
BBC
Hindustan Times

## Tuesday, September 24, 2013

### Pakistan earthquake and its new island

 A view of the new island off the coast of Pakistanfrom NBC
A magnitude 7.7-7.8 earthquake hit Pakistan today with an epicenter at about 15 km depth. It was well inside the borders of Pakistan and far from the ocean. Although only a few dozen (46) casualties have been reported as I write this (10:00 p.m. Central Time), the location of the quake is remote and it is likely that casualties will rise, with some estimates being in the thousands  (WAPMERR, The World Agency of Planetary Monitoring and Earthquake Risk Reduction). As this unfolds, an intriguing observation with speculations has hit the news--a mysterious island has risen from the ocean. It is reported to be 20-40 feet high and about 100 feet wide and lies about 350 feet out in the sea from the Gwadar coast (these numbers are very tentative--one report says that it's a mile out to sea, which seems more consistent with the picture that I've included above). It appears to be several hundred miles from the epicenter.
Residents of Gwadar have reported that an earthquake in 1968 produced an island that remained for about a year before vanishing (but it's reported also to have occurred in the 1940's so I don't know if this is an inconsistency in historical reporting or if it has happened more than once). What could have caused this mysterious phenomenon? Speculation at the moment is our old culprit, liquefaction--the sudden transformation of wet, but solid, sediments to a weak mush upon shaking, just like jiggling quicksand turns it to a mush (for more on liquefaction and the general phenomena discussed here, see my book "The Dynamics of Disaster" to be released by Norton Press on October 21!!). When this happens, structures such as buildings can sink into the ground because it can no longer support their weight.  The liquified material can also squirt up through cracks in the ground forming sand- or mud-volcanoes, and the speculation here is that the island is a big mud volcano.
This area of the Arabian Sea is known for its mud volcanoes.* Here the oceanic crust of the Arabian Sea is being subducted under Eurasia at a rate of about 4 cm/year.  A sediment pile has been building up on top of this subduction region to a thickness exceeding 6 km, a pile of wet gooey muck. The coastal region is known for mud volcanoes on land, and for the episodic formation of islands of them in the shallow waters off the coast. These are typically destroyed within months. Here's a seismic reflection image of a buried mud volcano from the reference * listed below:

Sometimes these mud islands appear in places that others have appeared before. One, called Malan island, appeared in 1999, unaccompanied by any noticeable earthquake, reoccupying a site of one that had been formed in 1945. It appears to have been driven by methane of bacterial origin.

One of the largest reported mud volcanoes is a complex 100-m high. It has been hanging around since at least 1840 and appears not to have changed much in the intervening decades. Methane of bacterial origin is persistently discharged into its crater mud lake. Eruptions of these gases often show periodicities of several hours that may be related to ocean tides. I'm not sure how the dating is done, but the article * below says that the presence of mud volcano activity in this region can be demonstrated for the last 460,000 years.

*G. Delisle, "The mud volcanoes of Pakistan," Environmental Geology, 46: 1024-1029, 2004.

## Friday, September 20, 2013

### Super Typhoon Usagi nears Philippines. What is a super typhoon?

 Cyclone Usagi on Thursday. Credit: Colorado State University
Hurricanes Ingrid and Manuel pummel Mexico; Hurricane Humberto in the Atlantic has become a ghost of its former self, and now Super Typhoon Usagi is targeting the Philippines and Taiwan.  It is expected to become merely a severe typhoon when it hits China, right at Hong Kong. Usagi has a diameter of more than 1000 kilometers. It has eclipsed Super Typhoon Utor, which was the strongest storm of the year so far. On Thursday evening, its minimum pressure was very low, 882 mb, which makes it the "deepest and most intense storm to exist on Earth since 1984 (tied with Wilma in 2005)" (quote from The Washington Post). As of Friday at 1:30 p.m. Pacific Time, the eyewall had undergone a replacement and winds have peaked in intensity, but the cyclone is still a very dangerous storm. It will weaken as it hits Taiwan, but is still expected to have winds near 100 mph when it hits Hong Kong (likely on Sunday, right when a major autumn festival is going on).

The past two decades, cyclone activity in the South China Sea has been relatively calm, and there are some forecasters worried that the population may "wrongly think that the typhoon risk in Hong Kong has declined." In 1906 and 1937 typhoons killed 15,000 and 11,000 people respectively, but with better warning systems, there have been less than two dozen casualties since the late 70's.

What is a super typhoon? It is equivalent to a Category 5 hurricane. Different ocean basins have different rating scales for their storms. Remember that in the Atlantic, big storms that rotate and have an eye are called "hurricanes." In the Pacific, they are called "cyclones." In most ocean basins, hurricanes are rated in "categories," with values assigned from 1-5. Here is a NOAA table of categories:
A "super typhoon" is defined as a storm that reaches maximum sustained winds of at least 65 m/s (234 km/hour), so it is equivalent to a Category 4-5 cyclone. The term "major hurricane" is also used, and it is used for storms that have maximum sustained 1-minute surface winds of at least 50 m/s or 180 km/hour, so applies to Category 3 storms and stronger.

## Thursday, September 12, 2013

### September floods in Boulder County, Colorado--monsoons

According to the National Weather Service, as of 8:20 a.m. this morning, Boulder has received 9.64 inches of rain this month, breaking the old record of 5.50 inches set back in 1940. Most of this rain fell overnight. The heavy rain resulted from warm moist air flowing in from the south colliding with cool moist air coming from the north and east. The pattern is expected to continue through the end of the week.
According to the National Weather Service, the "southwest monsoons" usually begin around the second week of July when an area of high pressure breaks away from the main Pacific ridge and settles in over the Great Basin, bringing hot temperatures during June and early July. This high center moves eastward across the Continental Divide and into the Central Plains (more or less what you see in the graphic above), followed by a slightly cooler but very moist environment brought in by southwesterly flow behind the high. The monsoon is typically over by the end of August, but can continue as late as October. To quote the NWS site "In fact, many areas in southwest Colorado and southeast Utah experience a secondary precipitation maximum in October due to late-season tropical storm moisture that's been carried northward by the monsoonal flow."
The monsoon moisture does not produce thunderstorms every day, but has a pattern of "bursts" and "breaks." A "burst" is a movement of a weak trough into the upper level westerly winds. It spreads upper level cold air into the region. Meanwhile, the lower levels of the atmosphere experience strong surface heating and transport of moisture from the southwest. These two conditions create a very unstable atmosphere, leading to widespread thunderstorm outbreaks.  A "break" occurs when an enhanced ridge of the Pacific subtropical high pressure moves inland and cuts off the moisture flow, thus stabilizing the atmosphere.
The monsoons are welcomed because they offer a break from accumulating hot days in June, but they also result in deadly flash floods. As I write this (3:00 PDT) flooding is leading to evacuations in Denver, I-225, I-270, I-70 and I-25 all are experiencing flooding and traffic jams, CU Boulder is closed today and tomorrow, and 5 dams are overtopping or burst. A life-threatening flood emergency has been in effect in Boulder and northern Jefferson counties since last midnight. Three people have been killed due to flooding, and lengthy flash flood warnings and watches are in place.

## Wednesday, September 4, 2013

### "The Big Problem with Disaster Planning"

Back in action after a much needed summer break!

About three months ago, Time Ideas (a section of the online version of Time magazine) asked me to write an article about problems with disaster planning. Now the copyright agreement allows me to post that article here:

We know that a tornado will bring howling winds and drenching rain, that a volcanic eruption will blanket the countryside with ash or lava, and that an earthquake will violently shake the ground. These are some ways in which Mother Nature unleashes the energy stored in the earth, and we can try to anticipate and prepare for the results. We can build basements and shelters to protect us from those tornadic winds, flee from the countryside when the volcano erupts, and reinforce our infrastructure from the quaking ground. But we have not always anticipated the chain reactions that these natural disasters often trigger.
The tornadic winds in Moore, Okla., last week and in Joplin, Mo., only two years ago killed many victims by blunt force trauma, but people also died from less direct causes. In Moore, it appears that at least six children, who should have been safe in a basement, died from asphyxiation when water, possibly from broken pipes, flooded to the low point where they were sheltered. Several people in Joplin died from a rare and difficult-to-treat fungal infection called zygomycosis. It turns out that people who have sustained massive traumatic injuries become so stressed that their immune systems find it difficult to fight off infections, paving the way for pathogens to enter the body and thrive. It took teams of experts from the local, state and federal level to figure out that the people who were displaying these symptoms had been impaled during the tornado by projectiles containing soil, and that the infections arose from a fungus in the soil.
In the harbor of Port-au-Prince, Haiti, much of the damage from the 2010 earthquake was not from direct shaking, but from the fact that the solid ground supporting the wharfs turned to mush during the quake, a process known as liquefaction. This, in turn, closed the harbor to rescue efforts to bring aid into the area. The same process caused multistory buildings in San Francisco to sink up to their second or third floors in the Loma Prieta earthquake.
And in the classic historic example of the eruption of the Icelandic volcano, Laki, in 1783, the tens of thousands of people who died as a result were mainly the victims of famine. Although the eruption was relatively small (a 6 on a volcanic scale of 8), the volcano spewed out around 8 million tons of hydrogen fluoride and 120 million tons of sulfur dioxide over an eight-month period. Half the cattle, 80% of the sheep and 20% of the people of Iceland died in the event now known as the “Mist Hardships.” The sulfurous clouds spread across Europe and around the world, weather patterns changed, crops failed and the deadly famines developed.
If we want to improve our odds of surviving disaster, we need to do two things. First, we need to be prepared for the rarest, biggest events. Currently we invest in infrastructure to protect us from the smaller events — be they tornados, eruptions, earthquakes or even small tsunamis that can be shut out by common storm wave barriers on exposed coastlines. But, we rarely have made the costly investments necessary to protect us from the rare, but truly devastating, big events.
Second, we need to learn much more about the secondary reactions and raise more awareness that it’s not just the primary disaster we have to anticipate. In order to enhance public safety, civic leaders and emergency responders as well as members of the general public must understand the links in the chain. By improving our emergency-response system and educating the public so that people are willing to support such efforts, we can greatly improve our readiness for the next inevitable outburst of Mother Nature.
Kieffer is a professor emerita of geology and physics at the University of Illinois at Urbana-Champaign and the recipient of a MacArthur Fellowship. She is the author of the forthcoming book Dynamics of Disaster and writes regularly on her blog Geology in Motion.

## Friday, August 16, 2013

### Earthquakes in New Zealand--why?

 Location of today's earthquake in New Zealand from this site. Note that the earthquake was on the South Island, whereas Wellington is on the southwestern tip of the North Island.
New Zealand has again been shaken by a series of earthquakes. The largest, at magnitude 6.5-6.6 struck Friday, and was followed by several smaller aftershocks with magnitude about 5.  Although these are "moderate" sized-earthquakes, they are capable of causing widespread damage if near population centers. Fortunately, these were not and, also fortunately, New Zealand has strict building codes. Even so, chimneys collapsed, roofs caved in, and a bridge collapsed on a major state highway. The earthquake was 94 km west of Wellington, the capital, at 10 km depth was fairly shallow. Bill Fry, a seismologist with GNS in Wellington said that the quake was similar to a 6.4 tremor that struck in the same area on July 21, and appears to be a continuation of a sequence that started with some of magnitude in the high 7's.
 Tectonic setting of New Zealandfrom Wiki here
The most powerful earthquake in New Zealand's recent recorded history, a magnitude 8.2, struck Wellington in 1855, although there are stories of earthquakes in the Maori legends. Wellington sits on the coast and was thrust upward so far by the quake that the shoreline receded 200 meters. Here is a great site with details of many of the major earthquakes.
New Zealand has a wide variety of active geologic phenomena--earthquakes, volcanic eruptions, geothermal areas, and landslides--because it sits at the boundary of the Australian and Pacific Plates. In the north (see graphic) the Pacific Plate is subducted under the Australian Plate, but in the south, the reverse happens: the Australian Plate is subducted under the Pacific Plate. These two subduction zones are connected by the Alpine Fault that runs along much of the west coast of the south island of New Zealand. Subduction rates are high--tens of millimeters per year, but so are erosion rates. The mountains rise about 10 mm/year, but are eroded down at about the same rate. The combination produces some of the most beautiful mountains in the world on the south island. The Alpine Fault is considered to be at high risk of producing a major earthquake in the next 40 years (see GNS).
Recent activity has been in the vicinity of the Marlborough fault system and, in particular, the M7.1 Canterbury (2010) and Christchurch (2011) earthquakes were on relatively minor faults. The fault system was named after the 1848 M7.5 earthquake centered in the Marlborough district of the South Island, a quake that produced substantial damage in the Wellington area as well. The European population of Wellington was approximately 4500 at the time; only 3 people died. Because stone and brick buildings suffered much more severe damage than wooden ones, for a time many buildings in the area were constructed of wood. But, after only 25-30 years, the institutional memory was lost and stone and brick buildings returned, partially encouraged by concerns about fire.  At the beginning of the 20th century the country seemed calm, and the New Zealand Official Yearbook included the comment: "earthquakes in New Zealand are rather a matter of scientific interest than a subject for alarm." Quote from this source. The population of Wellington in 2012 was 385,600.

## Sunday, August 11, 2013

### Mount Rokatenda (Paluweh) Volcano, Indonesia, erupts; six dead

 Mount Rokatenda in eruptionPhoto from BBC.com here
Mount Rokatenda*** north of the island of Flores in Indonesia erupted on August 10, killing 6 people. It has been erupting since late 2012. Eruptions were generally VEI 3 in intensity.  A 3 km exclusion zone was set up, and many residents of the island (~3000? according to an AP story) were evacuated, with many moving to the main island of Flores, but some refused to leave, growing used to the moderate volcanic activity.
 Paluweh and its eruption centersOriginally from Neumann van Padang, 1930as reproduced in his 1983 article
Scientific literature about this volcano is sparse, and the best that I found was "History of the volcanology in the former Netherlands East Indies" by Neumann van Padang, Scripta Geol. 71, pp. 1- 75, 1983. Reading this paper, with its four beautiful color plates brought back memories of the two famous photographers of volcanoes, Katya and Maurice Kraft who were killed in a pyroclastic flow during the eruption of Mount Unzen. Katya and I had roomed together at a field conference in the Caribbean.
The first sighting of this volcano appears to have been in 1856 by Francis, who called it Luca Raja; Buddingh in 1861 called it Palowe. When spotted by Kemmerling in 1921 it has a "partly barren, partly wooded summit."
Paluweh rises 3,000 meters from the sea floor, and is 875 m high above the water. It has the classic, though somewhat asymmetrical, stratovolcano conical structure though appears highly gullied from the topo map in Padang's figure 13. The summit region has a complex of small cones. These appear to be somewhat south of the main summit (see figure to the right). Documented eruptions were in ~1650, 1928, and 1972.
 March 31, 2013 NASA image of Paluweh/Rokatendashowing devastation on the south side of the island
##. Ash and pumice, estimated at 19.5 million cubic meters (corresponding to about 4.6 million cubic meters of lava) were erupted, and a new lava dome of about 8 million cubic meters as formed.
Paluweh erupted in August-September 1928. The eruptions took place from a collapsed area south of the summit where six ancient craters and three lava domes had been found. During the August eruption three new craters were formed, and a fourth on September 9th.  During the august eruptions there were "sea waves" with heights of 5-10 m (tsunamis) that attacked the island itself, killing 128 people out of the total population of 266.
Flores is near the eastern end of the Indonesian arc, west of East Temor and northwest of Darwin, Australia. The geology of Indonesia is extremely complicated. It lies at the intersection of three of the major lithospheric plates: the Indo-Australian Plate, the Philippine Plate, and the Eurasian Plate. These plates intersect at angles, leading to a complex network of faults in the region (and to the intense earthquakes that plague the area). These collisions produce deep trenches (Java, Timor, and Philippines Trenches) and island arc volcanoes.
 Simplified plate boundaries in Indonesia.From here.Although blurry, Flores can be seen just above theintersection of the Java and Timor Trenches.

***In researching this, I found different spellings: Rokatinda, Paluweh, Paloweh, Palu'e,  Luca Raja, Palowe. In the article referenced above, I think that the stratovolcano and the island that it occupies are referred to as Paluweh, and the summit crater as Rokatenda and I follow that nomenclature here. The "Palu..." names were Dutch origin; the Rokaa... names were the new Indonesian names. It is about 1250 miles east of Jakarta.

##The population now is estimated as about 10,000.

Here are other references to this volcano: The Smithsonian Global Volcanism Program here.
Volcano Discovery here.

## Thursday, August 1, 2013

### Steamboat geyser erupts!

 AP Photo/Robb Long
One of Yellowstone's most spectacular geysers erupted today, making headlines in major newspapers and radio news shows. Why such a fuss? Steamboat erupts to hundreds of feet, but only rarely and never predictably. Having worked in Yellowstone studying the geysers, I can imagine the excitement of the tourists as they hear the roar of the geyser erupting, see the towering plume, and perhaps get showered by its steam and droplets (hopefully not by any entrained rocks or sand). I wonder how many have glasses or camera lenses that now bear witness to the chemicals in Steamboat's water with fine deposits of minerals precipitated when that water evaporates?

What is a geyser? Is Steamboat really a geyser or should it be called a "hydrothermal explosion?" Geysers are usually defined as systems of hot water that intermittently ejecta some or all of their water into plumes consisting of water and steam. Geysers lie along a spectrum of thermal features that range from hot springs (warm to scalding) on one end and fumaroles on the other. A fumarole spouts dry or wet steam, usually continuously, but sometimes intermittently. Geysers can be thought of as hot springs that intermittently eject the hot water from their reservoirs.

The activity of a particular thermal feature in an area like Yellowstone depends on a delicate balance of heat and water (heat is supplied by hot water, vapor, or gases that rise from magma at depth; most of the water is circulating cool groundwater that is heated by the magmatic hot water or gases, or by contact with surrounding hot rocks). Too much water and you have a hot spring. Too much heat and you have a fumarole.  Just a right balance and you get a geyser that discharges and recharges its heat and water in cycles. (There are even cold "geysers" that charge and recharge carbon dioxide, but that's another story!)
 Conduit of Old Faithful

What does the reservoir of a geyser look like? We don't know for most geysers as it is difficult and dangerous to try to find out. However, in the 1990's, with the permission and assistance of the National Park Service, we lowered an ice-cooled miniature video camera into Old Faithful. This was in the days before truly miniature videos were available, and our system had to be less than 4" diameter to pass through a known constriction, had to contain its own lighting system, had to be cooled with ice because it was in an environment of 92 C steam, and had to have a heated lens to prevent condensation on the otherwise cool unit.  My colleague Jim Westphal at Caltech cleverly designed the system. From this work, we were able to constrict the cross-section of Old Faithful shown to the right. The reservoir is a tortuous series of narrow and wide spaces.  Researchers in Russia have probed geysers there and found similarly complex conduits, and it is likely that the reservoir of Steamboat Geyser is a similar complex of caverns and constrictions.

That word "intermittently"in the definition of a geyser is taken by many to mean "regularly" and somewhat "predictably." So, tourists get used to the fact that the National Park Service can tell them within about 10 minutes or so when Old Faithful is going to erupt; and within several tens of minutes or several hours for a number of the other geysers around Yellowstone.

So, what is Steamboat? It is a geyser if the word "intermittently" is used properly. But, the eruptions are so rare that they do resemble those rather nasty events called "hydrothermal explosions." The term "hydrothermal explosion" is usually used to describe a new feature--one that has popped up where no known feature, such as a geyser, existed before.  The vent of Steamboat is so large that it is well-known, and the boardwalk for tourists passes right by it so one can look down on its vent. But, just as some tourists probably got taken by surprise if they were close to Steamboat when this mighty eruption (reported to have been 200-300 feet high for 9 minutes) took off, tourists in the thermal basins are always at risk of a true hydrothermal explosion. That's one reason for staying on the boardwalks constructed for walking through these basins--they are built in areas deemed as safe as possible from future surprises.

**Reference: Hutchinson, R., Westphal, J., and Kieffer, S., In situ observations of Old Faithful Geyser, Geology, 25(10), 875-878, 1997.

## Wednesday, July 31, 2013

### Links between earthquakes and other geologic activity

Nature Geoscience (August volume 6(8), pp. 585-672) has a fairly long section ("a Web Focus") and a number of papers on geologic activity associated with or triggered by earthquakes. The introductory editorial reflects that in 1835 Charles Darwin voyaging on the Beagle experienced a large earthquake near Concepcion, Chile, and noted that within the hour a train of volcanoes in the Andes spouted out a dark column of smoke (though it would take a journey into Darwin's notes to determine whether he thought this was volcanic gas or perhaps debris from landslides. The implication in the editorial is that it was the former).

 Illustration of the elastic rebound part of volcanic arc subsidence after a megathrust earthquake
The first paper in this section (by Sigurjon Jonsson) summarizes the deflation of volcanic areas in response to the 2011 Tohoku and 2010 Maule (Chile) earthquakes. Both settings are at subduction zones (see figure), and the volcanoes that subsided were on the overriding plate. Prior to the earthquake, strain accumulates and compresses the overriding plate. During and after the earthquake, the overriding plate extends and subsides. However, subsidence beyond that which can be explained by this process is observed.
In the case of the Tohoku earthquake, Takada and Fukushima documented 5-15 cm of subsidence at a distance of 150-200 km from the rupture earthquake, but no volcanic eruptions. They suggest that subsidence is caused by sinking of magma reservoirs and their warm host rocks through the colder surrounding crust. Prichard and colleagues noted that two earthquakes (1906, 1960) were followed by eruptions in the Andes within a year, but that no eruptions have been clearly associated with the 2010 earthquake. They were, however, able to document the 15 cm of subsidence, and suggest that hydrothermal fluids were released from hydrothermal systems surrounding the volcanoes in Chile during the 2010 quake, and that the escape of these fluids caused the volcanic areas to deflate.
A second example of a proposed connection between earthquakes and geologic activity is more controversial: the Lusi mud volcano eruption. In 2006, mud erupted through and around a drill hole, flooding towns and displacing thousands of people.  Paul Davis summarizes a paper by Lupi et al. that proposes that the 2006 Lusi mud eruption in Indonesia (still continuing) was triggered by a M6.3 earthquake two days prior to the eruption and 275 km away.  Lupi et al. argue that strains, which are unarguably small at such a distance in homogeneous media,  were amplified by a downward concave layer of shale that acted as a parabolic reflector. Their simulations suggest that the stresses could have been about 100 kPa, five times higher than original estimates of 21 kPa. Such pressures, the assert, could have liquified the mud that resides at depth, resulting in the eruption of mud through the drill hole. This conclusion remains controversial (see discussion by R.J. Davies, et al., Earth and Planetary Science Letters, 272, 627-638, 2008).
For a third example, Fischer et al. examine subduction zone earthquakes as triggers of submarine hydrocarbon seepage.  Offshore of Pakistan, the Arabian Plate subducts beneath the Eurasian plate. This is a region of intense seismicity, in particular a major earthquake (M8.1) occurred there in 1945. It occurred in an area where gas hydrates (methane clathrates) are present, and leakage of hydrocarbon gas is known to occur here. Methane and sulfates both occur in the ocean with sulfate being stable above about 5 mbsf, and methane at greater depths. The concentration of both goes to nearly zero at a depth known as the sulfate-methane transition (SMT). In a complicated chemical reaction, sulphate is consumed through anaerobic oxidation of methane (CH4 + SO24�� ! HCO��3 + HS�� + H2O). Barium, being present in sea water, is precipitated at the SMT in so-called "barite fronts" and the abundance of barite can be used to reconstruct changes in upward methane flux.  The authors calculated that it would take approximately 38-91 years to produce the observed barite enrichments. This leads them to conclude that the barite production could have been initiated by the 1945 earthquake and an accompanying increase in methane flux due to release from the hydrates. If confirmed, submarine gas release triggered by earthquakes needs to be added to the list of processes that can add methane to the hydrosphere, and possibly to the atmosphere, in the carbon budget.

References: Takada, Y., and Fukushima, Y., Nature Geoscience, 6, 637-641, 2013.
Pritchard, M.E., Jay, J.A., Aron, F., Henderson, S.T., and Lara, L.E., Subsidence at southern Andes volcanoes induced by the 2010 Maule, Chile earthquake, Nature Geoscience, 6, 632-626, 2013.
Lupi, M., Saenger, E.H., Fuchs, F., and Miller, S.A., Lusi mud eruption triggered by geometric focusing of seismic waves, Nature Geoscience, 6, 642-646, 2013.
Fischer, D., et al., Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage, Nature Geoscience, 6, 647-651, 2013.

## Sunday, July 21, 2013

### Gansu, China, rain, mudslides, and now a shallow earthquake: are they related? And, was that shallow earthquake notice right?

 A map showing the location of the December 16, 1920 M 7.8 earthquake From Wiki here
An alert has just come out over the USGS earthquake network that there was a very shallow (1 km depth) magnitude 5.9 earthquake in Gansu province, China, 13 km east of the city Chabu (or, later reported as 156 km west of Tianshui.). Interestingly, two other agencies give very different estimates of the magnitude and depth: a 6.3 at 10 km depth by GFZ (at the Helmholtz Centre in Potsdam) and a 6.1 at 15 km depth according to EMSC (the European Seismological Centre), as reported here. And, while I was checking this on the EMSC site the numbers changed before my eyes to a M6.0 at 10 km depth! It would have been interesting to see how this all sorts out--if the USGS depth of 1 km is correct, this is a very unusual earthquake, and I wonder if it is actually an event associated with a major landslide rather than a fault zone (this was the case on May 18, 1980 when the north flank of Mount St. Helens failed into a big landslide). However, when I checked into the USGS site here, the depth is now listed at 9.8 km.  Makes me wonder what that earlier bulletin was all about!

The epicenter appears to have been Dingxi City. Dingxi is a "prefecture level city" in the southeast of Gansu province. It's area covers 20,300 sq. km, and the population is reported as 2.7 million people (in 1 urban district, 6 counties, and 119 towns). It was an important city in early development of some of China's cultures because the Wei River, one of the Yellow River's biggest tributaries, flows here.  The surrounding terrain hills and ravines cut into the loess deposits, weak sandy deposits, possibly water-saturated from the recent rains. This does not bode well for damage.

The earthquake occurred near midnight UTC on July 21. This follows, by only 8 days, a major landslide that reportedly trapped at least 100 tourists after a landslide cut off a road during a week of storms that have flooded rivers and triggered mudslides. At least 86 people were reported to have died by Chinese state media. Mudslides and floods are common in the mountainous areas of China, but this year seems to have been an especially bad one in many areas of Asia.

 Map showing the relation of todays earthquake to the major city of Tianshui.
In 2010, a deadly mudslide killed approximately 1500 people. After heavy rains, water built up behind a dam of debris that blocked a small river north of the city of Zhugqu. The dam broke, sending nearly 2 million cubic meters of mud and rocks through the town in a surge tens of feet high. A major problem in this area is that the forested areas have shrunk (by as much as 30% according to Wiki), and the reserve of timber has diminshed by 25% due to harvesting (these are 2010 numbers, and are relative to a base in the 1950's.) It is a region of massive construction of hydroelectric projects.

Gansu is also a region with many earthquakes.  In 1879, an earthquake with an estimated magnitude of 8.0 and Mercalli intensity XI (extreme) killed an estimated 220,000 people. This earthquake was preceded by foreshocks for a few days. The earthquake also triggered landslides that dammed local rivers up to 40-120 m.

Today's earthquake appears to be followed by numerous aftershocks, though it is difficult to tell where they are relative to the initial location given as 13 km east of Chabu. Some are reported at a distance of 156 km from Tianshui in Gansu province, a city of 3.5 million people.

Here is a site that is updating and comparing locations of today's quake, and that also gives earthquake locations since 1900 in this region.

## Thursday, July 18, 2013

### Heat Index vs. Humidex

 From this site
It is, at the moment, 91 F in my former home town of Urbana, IL, the dew point is 75 F, the relative humidity is 59%, and the Heat Index is 102 F! In Toronto, Canada, it is 33.3 C (92 F) in  the humidity is 46%, the dew point is 67 degrees and the Humidex is 40 C (104 F).

In contrast, where I live here near Seattle, the temperature is 73.7 F, and Weather Channel reports that "it feels like 77 F" (that's a jargon for the Heat Index.) The humidity is 57%, the dewpoint is 58 F.

What do these numbers mean, and how are they related to each other? First or all, a disclaimer: when I put those last numbers about temperature, dew point, and humidity into the NOAA government calculator that I cite below, I do not get the same answer as Weather Channel (77F); I get 74 F.  Either way, it's very comfortable here in the Pacific Northwest compared to conditions in the Midwest and eastern U.S. See below for further comments.

One difference is that Canadians use the Centigrade scale and we are stuck with the awkward Fahrenheit scale. However, it is possible to go back and forth between the two scales with some rounding off.  A simple way to interpret the Humidex is that it is equivalent to the dry temperature--that is, if the temperature is 30 C (86 F) and the calculated Humidex is 40 (104 F), then the humid heat "feels like" a dry temperature of 40 C (104 F).

The other differences are more complicated, and I have to say that--having lived in both countries--I had to laugh when I saw on Wiki that  "A joint committee formed by the United States and Canada to resolve differences has since been disbanded." Both scales use vapor pressure or dew point for the calculation, but the Canadians (perhaps because it is colder there?) use a dew point base of 45 F (7 C) for the humidex, whereas we Yanks use 57 F (14 C). The Heat Index, however, incorporates variables other than the vapor pressure, including
The Heat Index formula is:

$\mathrm{HI} = c_1 + c_2 T + c_3 R + c_4 T R + c_5 T^2 + c_6 R^2 + c_7 T^2R + c_8 T R^2 + c_9 T^2 R^2\ \,$
where the c's are constants, disputed by experts.

The Humidex formula is;
$\text{Humidex} = \text{Air temperature}\ +\ 0.5555 \times (6.11 \times e^{5417.7530 \times \left(\frac{1}{273.16} - \frac{1}{\text{dewpoint in kelvins}}\right)} - 10)$

The Humidex is higher than the US Heat Index at a given temperature and humidity. A mathematical scientist looking at these two formulas would instantly wonder two things: it's amazing that they are even close to each other because of the difference in form, and they must apply over very restricted temeprature ranges because of the nonlinear dependence on R (relative humidity) and temperature (T).

In terms of discomfort, the above graphic illustrates the various levels of discomfort and danger on a Heat Index scale. Here are the rough rules used by Canadian weather forecasters for Humidex:

Less than 29°C, no discomfort
30°C-39°C, some discomfort
40°C-45°C, great discomfort
45°C-54°C, dangerous
Above 54°C, heat stroke imminent

Here's a national weather site that allows you to use either F or C, and either Dew Point temperature or relative humidity, to calculate the Heat Index. (The numbers will be slightly off because of rounding errors.) Here's a commercial site for calculating Humidex. Note that by the U.S. Heat Index chart, our Seattle conditions at 73.7 F aren't even worth putting on the chart! And, my guess is that the reason the calculators that I provide here give wierd answers for the Seattle situation is that the formulas just aren't very good at these "low" temperatures.