The M7.1 and 6.4 Ridgecrest Earthquakes on the Airport Lake Fault Connect Owens Valley to the Garlock Fault
Abstract
The July 4-5, 2019 Ridgecrest earthquakes and their aftershocks extend from the southern end of the 1872 Owens Valley rupture to the north, southward to the Garlock Fault. The main events occurred on the Airport Lake fault (ALF), a dextral-oblique fault that previously had limited surface expression but was well known from subsurface studies. The surface rupture defines a path for the fault in great detail, illuminates the trace of the subsurface ALF, and is well expressed in surface geologic features along its entire length. In its northwestern exposures, the ALF appears to bifurcate into zones of contraction and transtension. Contraction is expressed northwestward as the White Hills anticline, a fold with at least 40-50m of structural relief in Pliocene strata, and by aftershocks. Transtension is manifest northeastward in sinistral-oblique, normal faults into the Wild Horse Mesa area. Aftershocks are mostly absent in the Coso volcanic field to the north, an area where the brittle-ductile transition is at a depth of only 4km. Seismicity continues northward from the Coso volcanic field where it merges with the Red Ridge fault, the southern continuation zone for the Owens Valley M7.9 earthquake. To the south, aftershocks trend southwestward along a mapped fault scarp active during the initial M6.4 event. Also, they spread westward and southward in the Spangler Hills in a zone of transpressional deformation evidenced both by mapped structures and by focal mechanisms.
With the M7.1 event, aftershocks extend southward to the Garlock fault, where they end. The southern continuation is well marked in Jurassic basement rocks to Holocene sedimentary cover. Across the Spangler Hills, the fault has what we interpret to be about 3 km of dextral slip. Southward, it extends across Teagle Wash and has numerous small scarps in Holocene surfaces, as well as being locally marked by a small playa lake. It cuts Pleistocene strata in the Christmas Canyon area where it has apparent offset of 100s of m to within less than 1km of the Garlock fault.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S34C..07W
- Keywords:
-
- 7299 General or miscellaneous;
- SEISMOLOGY