M 6.4 in the south Sandwich Islands (mmmm sandwich) 2014/3/11

While we were all excited about the local Gorda earthquake, there was an another interesting M 6.4 strike slip earthquake in the region of a recent series of earthquakes in the Scotia Sea. Sometimes earthquakes change the local stress field in the region of the earthquake and this may increase or decrease the stress of nearby faults. This “stress triggering” is short lived as the effects get spread out over time. The November 2013 earthquakes are recent enough that they may be blamed for triggering this M 6.4 earthquake, but that is pure speculation on my part. These fault systems are connected, but I have not done any modeling to determine if this is likely or not. One of the largest unknowns if he pre-earthquake stress on the fault that ruptured during this M 6.4 earthquake.

Please check out the pages I put together for the Scotia Sea earthquakes for more material on the regional tectonics here… There are some ascinating figures showing how this region was formed over the past few millions of years. The M 6.8 and M 7.8 earthquakes occurred along a strike slip fault system that links directly to the fault this M 6.4 earthquake may be located on. The M 7.0 earthquake occurred north of the M 6.8 and M 7.8, on another strike slip plate boundary fault. mmmm Sandwiches.

Here is a regional map showing the epicenter (in red and orange) with the plate boundary faults mapped in different colors.

Here is the Mww moment tensor for this earthquake. This shows the earthquake may be an east-west striking strike-slip earthquake, or a north-south striking strike slip earthquake.

Here is a local map showing the epicenter and the regional plate boundary faults. The largest orange dot is the epicenter for this M6.4 earthquake. There is an east-west green line that is a transform fault (strike-slip) nearest the epicenter. There are some north-south oriented faults (some magenta and some green). These are spreading ridges (extensional). Based on the tectonics here, I would interpret the moment tensor plotted above as a left-lateral strike slip earthquake.

Here is a regional map showing the modeled shaking intensity for this earthquake.

Here is the local map version of the shaking intensity map.

Here is a regional map showing the epicenter, along with a series of historic earthquake epicenters plotted as grey circles.

Here is the local map version of the epicentral map that includes the historic earthquakes.

Category(s): College Redwoods, earthquake, education, geology, plate tectonics, research

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