Applying Paleo-earthquake Data to Query for Earthquake Gate Areas

Egill Hauksson, & Men-Andrin Meier

Submitted August 14, 2017, SCEC Contribution #7617, 2017 SCEC Annual Meeting Talk on Tue 11:05

Over geological time, plate motion and associated tectonic processes have created the geophysical conditions under which the San Andreas Fault (SAF) operates. These conditions influence earthquake processes on both short and long time scales because rupture processes initiate locally and change the state of stress as they rupture. In turn over many earthquake cycles they evolve the long-term stress and frictional conditions of the SAF. For the last ~4 million years the San Andreas Fault (SAF) has accommodated approximately two thirds of the plate motion between the Pacific and North America plates in southern California. We investigate correlations between paleo-earthquake rupture models and modern geophysical data to search for possibly related variations in the geophysical data. Unusual stress state, seismicity, and fault complexities could be associated with initiation or termination of past ruptures, or earthquake gate areas. The two most prominent possible gate areas coincide with the two big bends in the SAF, near Gorman and White Water. The Mojave and San Bernardino segments that are not aligned with the plate motion appear to have three additional gate areas, including Cajon Pass. These gate areas that are imaged as changes in state of stress and seismicity may have been constructed by past earthquake ruptures predominantly approaching from the Chalome segment to the north or the Coachella Valley segment to the south. Alternatively, these gate areas have evolved over time as the SAF was shaped by long-term regional tectonics, including block rotations or underplating beneath San Gorgonio Pass. Reconciling modern geophysical data with paleo-earthquake data will improve understanding of earthquake rupture mechanisms taking place at different time and spatial scales. This effort will also improve our understanding of the rheology of the plate boundary system and may ultimately improve seismic hazard assessment.

Key Words
Paleoearthquakes, state of stress, seismicity

Hauksson, E., & Meier, M. (2017, 08). Applying Paleo-earthquake Data to Query for Earthquake Gate Areas. Oral Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
San Andreas Fault System (SAFS)