In July 2019, a series of earthquakes including two major shocks of magnitude 6.4 and 7.1 a day apart struck near Ridgecrest, CA, between Los Angeles and Las Vegas. For regional citizens, it was a violent disruption to the Fourth of July vacation. For seismologists, it was a rare opportunity to study how earthquakes harm the Earths crust.
The earthquake zone– which belongs to a network of faults called the Eastern California Shear Zone– is sparsely inhabited and arid, without much in the method of plants or buildings to obscure the surface area. However it is likewise well-covered by satellite and remote imagery and available to geologists who might be on the scene well before evidence of crust damage disappeared.
In July 2019, a series of earthquakes consisting of two major shocks of magnitude 6.4 and 7.1 a day apart struck near Ridgecrest, CA, in between Los Angeles and Las Vegas. For seismologists, it was an unusual opportunity to study how earthquakes harm the Earths crust.
They mapped the surface rupture from LIDAR data and aerial images collected by prior studies, and compared the rupture maps to other datasets to check out the distribution of rock damage from the earthquakes. This USGS animation shows the earthquake sequence starting a few hours before the series and continuing through July 8.
UC Davis doctoral trainee Alba Rodríguez Padilla was amongst the researchers studying the website, along with Professor Mike Oskin, Department of Earth and Planetary Sciences, Christopher Milliner, California Institute of Technology and Andreas Plesch of Harvard University. They mapped the surface area rupture from LIDAR data and aerial images collected by prior studies, and compared the rupture maps to other datasets to check out the distribution of rock damage from the earthquakes. Their findings are published today (February 24, 2022) in Nature Geoscience.
This USGS animation reveals the earthquake sequence beginning a couple of hours prior to the sequence and continuing through July 8. The M6.4 and its aftershocks are shown as a light blue star and dark blue circles, and the M7.1 and its aftershocks are revealed as a lavender star and red circles. Credit: United States Geological Survey
” We not only have aridity assisting here, enhancements in imaging strategy and resolution, together with collecting a big spatial information footprint, are what make the Ridgecrest coverage cutting edge,” Rodríguez Padilla said.
Inelastic deformation
The rock surrounding the fault struggled with “inelastic deformation,” indicating it was warped and broken instead of going back to its original configuration. The deformation was highest within 100 meters of the fault, with widespread, low-intensity damage approximately 20 kilometers (16 miles) away.
This deformation leaves the rock around the fault less stiff than previously, softening the crust. This softening dissipates energy from future earthquakes, increases permeability and focuses contortion.
The study supplies a better understanding of how damage from earthquakes builds up and may affect future occasions, Rodríguez Padilla said.
Recommendation: “Accrual of widespread rock damage from the 2019 Ridgecrest earthquakes” 24 February 2022, Nature Geoscience.DOI: 10.1038/ s41561-021-00888-w.
The study was moneyed by the Southern California Earthquake Center, which is supported by NSF and the U.S. Geological Survey. Rodríguez Padilla was partially supported by a NASA fellowship.