Contemporary tectonics, seismicity, and potential earthquake sources in the white mountains seismic gap, west-central Nevada and east-central California, USA

Abstract

Abstract The White Mountains seismic gap (WMSG) is a broad area between the 1872 Owens Valley earthquake and the 1932 Cedar Mountain earthquake that has a complicated tectonic setting and seismicity patterns, and is considered to have the potential for a strong or larger-magnitude earthquake in the near future. We take the Sierra Nevada block as the western boundary of the WMSG, the Pancake Range lineament and the southernmost 1932 earthquake ruptures as its approximate northern boundary, a change in structure, tectonic rates and seismicity level as the eastern boundary, and the northernmost 1872 earthquake ruptures as the southern boundary. Seismicity within the WMSG, especially in the southern part, has been at a very high level since 1978. This activity has included six events of magnitude ⩾ 6 and their associated aftershocks. In addition many earthquake swarms have occurred throughout the WMSG, some of which are distinctly located at the ends of fault zones or near changes in structural orientation. Focal mechanisms show a predominance of strike-slip solutions for both small and large earthquakes, with NW-trending right-lateral and NE-trending left-lateral solutions for over half of the mechanisms. These are similar to the sense of displacements and orientations of the larger faults in the WMSG. Thus seismic strain is consistent with the faulting pattern in the WMSG and is accommodating contemporary deformation through a conjugate set of strike-slip and normal-oblique-slip faults. Examination and analysis of eighteen of the larger faults in the WMSG leads to the estimation of characteristic earthquakes ranging from magnitude 6.8 to 7.4. Given the size of the seismic gap (100 km) and the pronounced change in structure near the middle of the seismic gap, it seems likely that it will require two or more magnitude ~ M 7 + events to “fill” the gap.