Science Highlights 2010 - UNAVCO Event Response - Mw=8.8 Chile Earthquake Feb. 27, 2010 | UNAVCO Relevant Data Supersite UNAVCO is hosting the GEO (Group on Earth Observations) Supersite on the 2010 Chilean earthquake, featuring a variety of maps, images, and data. UNAVCO Event Response Forum For information on accessing data including high rate GPS, SAR data, seismic data from the PBO network, UNAVCO GPS equipment availability, and borehole strainmeter data from the PBO network go to our Event Response Forum. GPS Data Available from NASA/GNN Station SANT for Earthquake UNAVCO operates the NASA/GGN GPS station near Santiago (SANT), which is a high rate station set to log at 1 Hz (Fig. 12). The Great Earthquake of Feb. 27th, 2010 A magnitude 8.8 earthquake occurred at 3:34 AM local time (06:36 UTC) off the coast of the Maule region of central Chile. Tectonic Setting of this Event This megathrust earthquake resulted from the release of mechanical strain where the Nazca tectonic plate is being subducted beneath the South American plate. Community Response unavco.org. Community Scientists Dr.
Ground Truth Trekking Blog » Largest Earthquakes since 1900 This is largely a repeat of part of my post following the 2010 Chile Earthquake, with a few updates and clarifications. Edit: I changed the earthquake magnitude from 8.9 to 9.0 reflecting the USGS’s catalog (as of 16 March 2011). What are the chances? Global occurrence of large earthquakes Does it seem like there are a lot of big earthquakes lately? Haiti, Chile, New Zealand, and Japan have all seen devastating earthquakes in the past 15 months. There is almost certainly no connection between the earthquakes in Haiti and New Zealand and other distant earthquakes. However, the largest earthquakes – those over magnitude 8 – do seem to cluster in time. We’ve been measuring earthquakes since 1900, and the recurrence of the largest ones doesn’t seem random. Click the graphic for data and vector graphic file. And the past decade has been a big one for earthquakes. What does this mean? Why do the biggest earthquakes come in clusters? At this point we don’t really know.
Understanding the Christchurch Earthquake of 22 Feb 2011: magnitude, location and impact | Posts from Keith Woodford Last September, those of us who live in Christchurch experienced a 7.1 earthquake. Since then, we have referred to that as ‘the big one’, confident that we would never again experience anything similar. In that September quake, there were no lives lost, but there were many houses badly damaged and destroyed. Well, everything has now changed. I do not intend to write here of the overwhelming human tragedy. We read in the media that this was a 6.3 earthquake on the Richter scale. (For those who are interested in the maths of the above numbers, the Richter Scale is logarithmic to base 10; also the energy released is a function of amplitude to the power of 1.5. The strength of the Richter scale (or more accurately the Modified Magnitude Scale) is that it provides an objective measure of the shaking amplitude and hence energy release. The key measure of intensity at a particular location is the ground acceleration. Like this: Like Loading...
Understanding the Christchurch earthquake: building damage | Posts from Keith Woodford There are many puzzles as to why some of Christchurch’s buildings have survived the 6.3 earthquake of February 2011, and others have not. However, a combination of observations plus document-searching does provide some answers. In terms of magnitude, this was just a moderate earthquake, but the local effects on Christchurch have been huge because of its proximity and shallowness. Even within Christchurch, location was of huge importance, but there is more to it than that. It seems that we do indeed have very stringent building codes in New Zealand. Not only are the codes stringent, but they are enforced. Having planned the building of a new house both in Australia (in the 1980s) and in New Zealand ( in 2001), I know that the building code is a lot stronger here in New Zealand than in Australia. The messages from the 7.1 ‘dress rehearsal’ earthquake on September 2010 seemed reasonably straightforward. Unfortunately, a house with a concrete pad that has cracked and split is history.
Tectonics of the M7 earthquake near Christchurch, New Zealand | Highly Allochthonous This post was written in response to the Darfield earthquake in September 2010. The most recent seismic activity is discussed here. [Updated 8th September 1200 GMT – see bottom of post. The South Island of New Zealand has just been shaken by a large earthquake, reported as a magnitude 7.0 by the USGS. Focal mechanism of September 3rd earthquake, and it's location with respect to the plate boundary in New Zealand As the figure above illustrates, New Zealand is not just located on top of the boundary between the Pacific and Australian plates: it is located at a point where the nature of that plate boundary changes in some rather fundamental ways. New Zealand is a region of distributed deformation: the relative motions between the Australian and Pacific plates are not accommodated on one or two faults in a narrow zone, but on many faults across a much wider zone. Update: 4/9/10 Here’s a couple more plots to that help to further put this earthquake in context. Some other useful links:
Earthquakes and Plate Tectonics The world's earthquakes are not randomly distributed over the Earth's surface. They tend to be concentrated in narrow zones. Why is this? And why are volcanoes and mountain ranges also found in these zones, too? An explanation is to be found in plate tectonics, a concept which has revolutionized thinking in the Earth's sciences in the last 10 years. Plate tectonics tells us that the Earth's rigid outer shell (lithosphere) is broken into a mosaic of oceanic and continental plates which can slide over the plastic aesthenosphere, which is the uppermost layer of the mantle. The lithosphere covers the whole Earth. One of the keys to plate tectonics was the discovery that the Earth's magnetic field has reversed its polarity 170 times in the last 80 million years. Using these magnetic strips as evidence of movement, it became obvious that the Earth's surface consisted of a mosaic of crustal plates that were continually jostling one another. How are earthquakes connected with plate tectonics?
Expert: Haiti quake occurred in complex, active seismic region January 14, 2010 The magnitude 7.0 earthquake that triggered disastrous destruction and mounting death tolls in Haiti this week occurred in a highly complex tangle of tectonic faults near the intersection of the Caribbean and North American crustal plates, according to a quake expert at the Woods Hole Oceanographic Institution (WHOI) who has studied faults in the region and throughout the world. Jian Lin, a WHOI senior scientist in geology and geophysics, said that even though the quake was “large but not huge,” there were three factors that made it particularly devastating: First, it was centered just 10 miles southwest of the capital city, Port au Prince; second, the quake was shallow—only about 10-15 kilometers below the land’s surface; third, and more importantly, many homes and buildings in the economically poor country were not built to withstand such a force and collapsed or crumbled. All of these circumstances made the Jan. 12 earthquake a “worst-case scenario,” Lin said.
File:Okhotsk Plate map en.png New Zealand Earthquakes: locations, depths and tsunami | Posts from Keith Woodford More detailed investigation of earthquake-related documents has now led me to write something further about earthquakes in New Zealand. (For earlier posts about the Christchurch earthquakes see in the earthquake category.) I have found four GNS maps (www.gns.cri.nz) which, when brought together, seem fundamental to understanding the ‘big picture’. The first map (above) shows the three major fault systems in New Zealand: the North Island System, the Marlborough System and the Alpine Fault. The picture above shows where the major shallow earthquakes have been in the last 160+ plus years. The third map (above) shows all of the shallow earthquakes of more than Magnitude 3 over a ten year period. This last map (above) provides key information of several things. So what does all of this mean? My second interpretation is that the Hikurangi Trough provides our greatest risk for a tsunami. I indicated earlier that I would say more about Wellington. Like this: