Seismic Evidence for Splays of the Eureka Peak Fault beneath Yucca Valley, California

In April 2015, we acquired high-resolution P- and S-wave seismic data along a 3.1-km-long, E-W-trending profile in Yucca Valley, California. Our seismic survey was designed to locate possible sub-parallel faults of the Eureka Peak Fault, which trends NW-SE near the western end of our profile. The Eureka Peak Fault is a potential hazard to the Yucca Valley region, as it appears to have experienced surface ruptures associated with both the 23 April 1992 M 6.1 Joshua Tree earthquake and the 28 June 1992 M 7.3 Landers earthquake. We simultaneously acquired P- and S-wave data using explosive sources spaced every 100 m, along with higher resolution P-wave data from seisgun sources spaced every 5 m. Each shot was co-located with and recorded by 634 P-wave geophones (40-Hz) spaced 5 m apart and 250 S-wave geophones (4.5-Hz) spaced 10 meters apart. We developed P-wave tomographic velocity models and reflection images that show at least one significant fault about 2.3 km NE of the Eureka Peak Fault. This fault may potentially pose a hazard and affect groundwater flow in the area.