A High Density Seismic Hazard Survey in the Los Angeles Basin

Abstract

We are finalizing plans for a large-scale seismic hazard survey of the Los Angeles sedimentary basin for the purposes of determining near-surface (0 to 4 km) velocities, basin structure, microseismicity, and the structure of the underlying crust. The survey will be valuable for creating densely sampled micro-zonation maps of seismic hazards for infrastructure resiliency and for providing better velocity models for strong motion modeling. The survey may reveal structures that show some hydrocarbon potential as well has image the aquifer system in the basin. This large number of sensors (Large-N) passive seismic survey will sample the basin at 10 sensors per square kilometer, which is about an order of magnitude less dense that a standard industry 3D survey, but would provide ample coverage for determining the basin structure and the 3D velocity variations. The survey will have about 18,000 receiver positions that will be occupied by a rolling grid of 5000 sensors, each occupying a given position for 30 days of passive recording. It will take approximately 4 months for this array to traverse the basin. There will be a fixed array of 200 three-component nodes that will record for the entire duration of the survey. In addition, we are planning on 60-70 deep hole (50m +/-) explosive charges to help determine the shallow P-wave velocities, and to look for possible reflections. Data products resulting for the survey will be a shear-wave (Vs) model from surface to 2 to 3 km (to be used for Vs100 and deeper Vs for ground motion prediction modeling), P-wave (Vp) model from surface to 4 to 5 km, passive and active reflection imaging, seismicity, sedimentary basement and Moho imaging using receiver functions, and more. Initially, the raw data will be shared with researchers, government, and supporters before being made public.

AAPG Datapages/Search and Discovery Article #90339 ©2019 AAPG Pacific Section Convention 2019, Long Beach, California, April 1-3, 2019