Analysis of Triggering of Earthquakes and Tremor in the Western U.S. due to the 2010 El Mayor Cucapah Earthquake and the Mw6.8 Mendocino Triple Junction Earthquake in 2014

Abstract:

Recent studies indicate that the passage of seismic waves from large earthquakes are able to trigger small earthquakes and tremor at regional distances. These small events may be detected by applying a high-pass filter to seismograms to remove the much larger ground motion amplitudes from the large distant earthquake. Our interests are in examining the local triggering of earthquakes and tremor throughout the West Coast of North America from the magnitude 7.2 El Mayor-Cucapah 2010 earthquake and the magnitude 6.8 Northern California, March 10, 2014 earthquake, just north of the Mendocino Triple Junction. We will present the results of the analysis of waveform data from hundreds of seismometers throughout Southern California, Northern California, Oregon, Washington, as well as some stations bordering these states. Our preliminary results suggest that triggering of local earthquakes and tremor occurred for both earthquakes. In the case of the records of the Southern California stations for the El Mayor Cucapah 2010 earthquake, 27 stations showed triggering near the seismic station. 13 of these stations are located in or near known geothermal areas, while others were located along active faults and one offshore. While conducting this study, we detected an instrumental noise signal present in 63 of the Southern California seismograms for the El Mayor-Cucapah earthquake. Initially, the signal looked like a typical triggered event, yet with further investigation we found its likely cause to be instrumental noise. We plan to relate our observations of triggered seismicity and tremor to the tectonic environment to test the hypothesis that triggering and tremor most commonly occurs in volcanic and geothermal areas.