Detailed fracture map and orthophoto of the southern portion of the M6.4 2019 Ridgecrest Earthquake

Alana M. Williams, Ian Pierce, Rich D. Koehler, Sinan O. Akciz, Colin Chupik, & Jayne M. Bormann

Published August 15, 2019, SCEC Contribution #9886, 2019 SCEC Annual Meeting Poster #223

An M6.4 foreshock struck on July 3, 2019, near Ridgecrest, California, and ruptured bilaterally. The mainshock, An M7.1 event, followed this earthquake on July 5. Between July 4 and July 9, low altitude aerial photos were acquired along ~12 km of the M7.1 and ~8 km of the M6.4 Ridgecrest earthquake sequence surface ruptures south of CA 178. Structure-from-motion (SfM) was used to produce georeferenced orthophoto mosaics (~2-20 cm/pixel) along both ruptures. This basemap was used to map the details of the surface trace at scales ranging from 1:40 to 1:150 (depending on the resolution of the orthophoto) and plot the locations of the lateral offset measurement locations. The M6.4 also ruptured an orthogonal portion of the fault that slipped in the M7.1 mainshock. The overall surface rupture pattern consists of a prominent mole track with a maximum vertical height of ~20 cm and left-stepping en-echelon faults with steps ranging from a few to hundreds of meters. The rupture width varies from <10 m to >50 m. Locally, the fault exhibits both compressional and extensional features such as grabens, vertical scarps, and thrusts. The fracture patterns are highly variable with several conjugate faults and structural complexities such as horsetail splays, releasing bends, and restraining bends.

Key Words
Ridgecrest, mapping, fault, california

Citation
Williams, A. M., Pierce, I., Koehler, R. D., Akciz, S. O., Chupik, C., & Bormann, J. M. (2019, 08). Detailed fracture map and orthophoto of the southern portion of the M6.4 2019 Ridgecrest Earthquake. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes