A magnitude 7.4 earthquake struck the state of Oaxaca, Mexico at 12:02 local time, 20 March 2012. This region is above a tectonic plate boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr. Moderate to very strong shaking was experienced throughout an area within 100km of the epicenter.

24 minutes later, the seafloor pressure sensor on CORK 1026B at our Cascadia Basin (formerly ODP 1027) location sensed the pressure waves as they propagated through the earth. This trace shows these observations:

For more information:

USGS Info Page
Wikipedia Info Page
Data Trace in our Plotting Utility (login required)