RAPID - Afterslip and triggered slip associated with the Ridgecrest earthquake sequence

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When they occur, major California earthquakes result in billions of dollars damage. Greater awareness of earthquake risk follows each event, and also accompanies scientific efforts to further understand seismic processes. This RAPID is motivated by the need to quickly deploy instruments on active faults near the July 2019 Ridgecrest earthquakes to determine how the earthquake have stressed nearby active faults. The plan is to install six extensometers and to quantify the potential for present and future slip on nearby faults. Data will be acquired once per minute and stored for public access at UNAVCO.This works is motivated by the need to urgently deploy extensometers on active faults near the meizzocenter of the Ridgecrest earthquake sequence to determine whether, and how, stress changes in the earthquake have stressed nearby active faults. Stress changes tend to set up a logarithmically decaying creep rate on nearby faults following triggered slip that can be measured using sensitive extensometers. The seismic sequence itself was a cascade of conjugate ruptures with progressively greater magnitude followed by thousands of smaller aftershocks as a nearby lattice of conjugate faults relaxed epicentral strain. The dynamic stresses from the earthquakes had extreme reach, causing slip to be triggered on faults as far south as the Mexican border. The deployment of 6 new extensometers supplement and existing one deployed across the surface rupture two days after rupture. The extensometers record slip with an accuracy of 2 micrometer over a range of 2-4 meters and sample once per minute for a year. The extensometers will record slip data for a year, which will allow for calculating rate changes and to search for episodic slip that can be used to determine rheological conditions in the fault zone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.