2015.09.16 Chile Update #1

Here are some updates to this earthquake and tsunami.
First, here is an updated map. I have included an illustration from Atwater et al. (2005) that shows the earthquake cycle at a subduction zone. A subduction zone is a convergent plate boundary where the oceanic crust of one plate subducts beneath the continental crust of another plate. In Chile, these are the Nazca and South America plates, respectively. The earthquake cycle causes the continental crust to deform elastically. When the fault slips (the earthquake), the seafloor deforms, elevating the water column. When the water column converts this newly stored potential energy into kinetic energy, it falls down and then oscillates up and down. This oscillation creates waves that spread out across the ocean. These waves are the tsunami waves.

I include tsunami travel time information on the above map. The travel time map comes from NOAA here. The tsunami height observations come from here.
Here is the latest estimate for when the first tsunami may reach the west coast of the USA. This came from the National Tsunami Warning Center from Palmer, AK.

Here is the tsunami travel time map from NOAA.

Here is a modeled estimate of tsunami wave height from the NTWC in Alaska.

The largest aftershock, so far, is a M = 7.0 earthquake. I include the moment tensor for that earthquake. Check out my first post about the M 8.3 earthquake to learn more about moment tensors.

    Here are the USGS web pages for these two earthquakes:

  • 2015.09.16 M 8.3
  • 2015.09.16 M 7.0
  • There are a number of M ~ 6 earthquakes and here is a link that will take one to the USGS web pages for those earthquakes. Just click on the circles and a little window shows up with a link to that earthquake page.

Here is an update to the observation of the HSU “Baby Benioff” in Van Matre Hall (photo credit Dr. Mark Hemphill-Haley, chair of the Humboldt State University, Department of Geology. Here is the HSU Dept. of Geology facebook page. Mark’s photo shows the P-wave. The video below shows the secondary waves.

This is a video of the seismometer as secondary waves (please help here) propagate through the Earth. Here is a link to the 17 MB mp4 file if the embedded video below does not work. h/t to Hector Flores, a Geology student at Humboldt State University for providing this video. Here is his email: hef49 at humboldt.edu

There was also a video from youtube that shows a seiche in a swimming pool. (h/t/ Hillary on facebook).

The PAGER alert has also been updated and now has a slightly higher estimate for potential casualties. Below I post two PAGER alert versions (V3 and V6). These PAGER alerts are generated by numerical models. As seismologists further analyze the seismic data, they improve their models and generate new PAGER loss estimates. These loss estimates allow governments to estimate how much aid that they might need to prepare.

Also, the USGS has prepared their first fault plane solution. This is one of the updates to the numerical models that led to changes in the PAGER alerts (and other derivative, like intensity and PGA maps). This is posted on the USGS web page for the M 8.3 earthquake.

Here are some other examples of updates to the seismic data and models.
PGA V 1:

PGA V 2:

Attenuation V 1:

Attenuation V 2 (note that one of the major changes occurs at observations with short hypocentral distance, also, note the difference in horizontal scale):

Here are some seismicity plots from Centro Sismologico Nacional Universidad de Chile. There is a map and two cross sections.

P 14

P 15

Here are two animations from IRIS. These animations allow us to visualize seismic waves propagate through the Earth. I present screenshots of each animation above each embedded animation.
This shows motions in three directions.

Here is a link to the mp4 file if you want to download it.

This shows motion in the vertical direction.

Here is a link to the mp4 file if you want to download it.

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