Station Delays, Their Standard Deviations, and Event Relocations in the Reno-Area Basin from a Dense USArray Flexible Array Deployment during the 2008 West Reno Earthquake Swarm

Abstract

The seismic hazard of a sedimentary basin is high. The basin depth and its geometry control the amplification of ground motion. So from the point of earthquake hazard, it is important to know the basin geometry and its depth for the hazard evaluation of an area. Knowing the basin geometry and depth and velocity of sediments will enhance our understanding of ground amplification to improve seismic hazard evaluations. In this context, to evaluate the seismic hazard of the Reno Basin, the Nevada Seismological Laboratory (NSL) conducted a citizen volunteer Reno Basin multiple instrument temporary deployment using USArray Flexible Array single-channel RefTek RT-125A (Texan) recorders. Stations were deployed at 106 locations in the Reno Basin during the May-July 2008 period of the 2008 west urban Reno Mogul earthquake swarm. This was a very dense deployment as the basin only occupies about 150 square kilometers. The Flexible Array deployment supplemented recordings from 46 NSL/ANSS regional network stations, Reno area strong-motion, and 12 IRIS RAMP stations. This allowed relocation of 97 events in the West Reno/Mogul sequence during May-July 2008, using phase arrivals on all network and volunteer Texan stations. Hypoinverse runs showed no less location error with added Texans, but visually, the events are drawn into tighter clusters. An average station delay map, a mode-of-station-delay map, and a map of the standard deviations of the average station delays confirm that the western part of the basin is thickest. Negative delays and high standard deviations in delay times in the Verdi Basin confirmed the basin to be narrow and complex.