Measuring Aseismic Slip through Characteristically Repeating Earthquakes at the Mendocino Triple Junction

Kathryn Materna, Taka'aki Taira, & Roland Bürgmann

Published August 15, 2017, SCEC Contribution #7703, 2017 SCEC Annual Meeting Poster #216

The Mendocino Triple Junction (MTJ) is located at the seismically active transition between the San Andreas fault system, the Mendocino Transform Fault, and the Cascadia Subduction Zone. Most of the major faults of the triple junction are located offshore, making it especially difficult to characterize the patterns of interseismic coupling and aseismic creep that are important for hazard analysis. In this work, we study aseismic creep rates near the MTJ using characteristically repeating earthquakes (CREs) as indicators of creep rate. Using seismic data from 2008-2017, we identify CREs as recorded by an array of eight 100-Hz borehole seismometers deployed in the Cape Mendocino area. We apply a repeating earthquake detection criterion to the waveforms, and identify several dozen sequences of repeating earthquakes that are persistent over time. The CRE data implies a creep rate of ~3 cm/yr on the downgoing extension of the Mendocino Transform Fault, consistent with estimates of coupling on other oceanic transform faults. We also find repeating earthquakes on the southern margin of the North American accretionary wedge. In connection with a M5.7 earthquake occurring on the Mendocino Fault Zone in 2015, we find that repeating earthquakes in different locations showed increases or decreases in activity surrounding the event. These results provide on-shore evidence for significant aseismic creep on an oceanic transform fault, and show that CREs can help assess time-dependent changes in creep behavior in this fault system.

Key Words
Repeating earthquakes, aseismic slip

Citation
Materna, K., Taira, T., & Bürgmann, R. (2017, 08). Measuring Aseismic Slip through Characteristically Repeating Earthquakes at the Mendocino Triple Junction . Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)