Major earthquake causes extensive damage in Christchurch, New Zealand

Map of felt effects of the Christchurch earthquake
from Geonet

Update at 11:00 a.m. on 2/23/11:  Dave Petley's landslide blog here has an excellent summary of reasons that this quake was so devastating compared to the higher-magnitude September event.

Mid-day, Tuesday, a major earthquake struck 10 km south-east of Christchurch, New Zealand.  The focal depth was shallow, only 5 km.  The USGS called it a magnitude 5.5; the press and Geonet are saying that it is a 6.3.  65 people have been reported killed at this time, the toll is likely to go higher, and damage is extensive. There has been at least one strong aftershock.

The graph is a preliminary summary  of damage, keyed to the Modified Mercalli intensity scale.  MM8 (dark orange) is heavily damaged, light orange is damaging, yellow is slightly damaging, and green is strong. The red square marks the epicenter.  Click on the Geonet link in the caption to get an updated version of this map.

In an earlier post, I discussed the damage caused by the September 3, 2010, M7.1 earthquake, also near Christchurch. A lot of the damage then was caused by liquefaction, and that is likely to be a problem this time as well.  Many buildings had been damaged by the earlier earthquake, repairs had not been completed, and so they were vulnerable to the intense shaking that occurred.

There is more information on Dave Petley's Landslide Blog, and a good discussion of the geologic setting on Chris Rowan's Highly Allocthonous blog. Information, including some videos, is starting to come in to CNN.COM.  This one shows a bit of footage taken during the earthquake at the very beginning of the video.

Our thoughts and sympathies go out to our Kiwi friends.

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Christchurch Earthquake and Liquefaction

A magnitude 7.1 earthquake centered 30 km west of Christchurch, New Zealand, at a depth of 10 km occurred at 4:35 a.m. local time on Friday, September 3, 2010.  Strict engineering codes prevented any loss of life, but damage to buildings and to underground infrastructure was severe.  Strikingly, Christchurch sits some distance to the east of the major active fault on the South Island, the Marlborough Fault Zone, a transform fault like the San Andreas.

Auckland's waterfront is built on reclaimed land, saturated with water, and large sections of the city laid on soft sediments which remained saturated with water from the New Zealand winter. Whole areas of the city were transformed from firm land to muddy sludge. Water from the sediments squirted up through the soil during and after the quake, damaging as many as 9/10 of the homes on the flats. In one relatively new subdivision, Bexley, over 100 new homes were left unhabitable.  Where the water concentrated into small cracks, mud poured to the surface forming mud volcanoes (photo). A video showing the mud and damage from liquefaction is available here, and an explanation of liquefaction is available here.

If you don't think that life can change in a second, dig this!

Cows stranded by earthquake/landslide New Zealand from NPR

AP wrote a story about these stranded cows and called it "Nowhere to Moove." At this time, it's not clear what the fate of these cows is/will be.
   I won't try to summarize the science of the November 14 New Zealand earthquake, but recommend Temblor by David Jacobson and Ross Stein. There were 2 deaths and a 6-8' high tsunami on the east coast of the South Island. The earthquake was about 60 miles north of Christchurch. Temblor reports that it was not one fault that ruptured, but four, including one that had not previously been recognized in Waipipi Bay. Displacement reached 33 feet. See the Temblor site for some spectacular pictures.

UPDATE on 11/15: Cows have been rescued!! 

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 Zealand
from 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.

Are deep waters ultramarine blue?

Artists impression of an S3- molecule in a diamond cell.
The rich blue color is that of the mineral lapis lazuli, and is due
the S3- molecule.
Credit: Copyright Pokrovski and Dubrovinsky as shown in
Science Daily here

Aside: Dave Petley has updated his landslide blog with excellent coverage of the conditions in Christchurch.


Sulfur is a key element in the transportation of gold in hot water geothermal systems.  Although there are a number of forms, the most common are sulfide (sulfur in a -2 oxidation state, hydrogen sulfide, H2S) and sulfate (SO4, in which a sulfur ion in a +6 oxidation state is surrounded by four oxygens in a tetrahedron).  It has been difficult to characterize the chemistry of the hot aqueous fluids because rates of reaction are too fast to allow the hot fluid to preserve its chemistry upon cooling.  Attempts to deduce the chemistry by looking at fluid inclusions trapped in minerals have been frustrated by these reactions, and reveal almost exclusively sulfate and sulfide.  In a paper in the February 25, 2011, issue of Science, (vol. 331, p. 1052), Gleb Pokrovski and Leonid Dubrovinsky used Raman spectroscopy to examine the species in situ in a diamond anvil cell at temperatures between 25 and 450 C, and pressures of 0.5-3.5 GPa, temperatures and pressures characteristic of hydrothermal systems.  They found that sulfate and sulfide were the dominant species at temperatures less than 250 C, as expected, but that at higher temperatures the dominant form was trisulfur, S3-.  It was identified by S-S bending and stretching modes at characteristic wavelengths in the Raman spectrum.

Combined with known thermodynamics, the data allowed them to predict the S3- concentrations in natural fluids, they calculate that in a 1 wt% S concentration, the S3- accounts for a major part of the dissolved sulfur over a wide range of conditions of pressure, temperature and pH.  S3- forms at the expense of sulfides and sulfates, and thus reduces the amount of sulfur retained in deposited minerals such as pyrite, pyrrhotite, anhydrite and barite. It increases sulfur mobility by preserving it in the aqueous solution. It binds well with gold, copper and platinum, and so competes with sulfide and sulfate as a transporting agent for these elements at depth.  Upon rising into lower pressure and temperature environments, it will decompose into sulfate and sulfide, resulting in precipitation of the gold.  It may rise high enough to form a low-density vapor phase. Finally, Pokrovski and Dubrovinsky conclude that if S3- is as abundant as they predict, it will influence the thermodynamic properties, kinetic models of reactions, and sulfur isotope-fractionation models which ignore its formation at this time.

In an accompanying perspective (p. 1018), Craig Manning discusses the role of S3- in mineralogy, specifically the role of it in giving lapis lazuli it's deep blue color by charge transfer between groups of S3-.  Because sulfur has such different oxidation states (6+ and 2-)  changes between these states leads to the transfer of many electrons. These transfers can lead to oxidation or reduction reactions in host rocks. He notes that in the 1991 eruption of Mount Pinatubo more sulfur was degassed than could be accounted for by the chemistry of the parent magma. The simplest explanation is that there was a sulfur-rich vapor phase deep in the volcano that was carried upward in the eruption, and that much of the SO2 released could have formed from precursory aqueous S3-. Manning concludes with the intriguing thought that deep waters may be ultramarine blue, an old idea dating back to 1856, revived by  by Walter Giggenbach in 1971, but attributed to S2-, not S3-.