Seismic Structure Imaging of San Andreas Fault Zone by Scattered Waves From Local Earthquakes at Parkfield, California

Session: Seismic Imaging of Fault Zones
Type: Oral
Date: 4/29/2020
Time: 03:15 PM
Room: 215 + 220
Description: 

Seismic imaging with active seismic sources can be used to image subsurface structures such as faults, fractures and layer interfaces with higher resolutions than seismic tomographic methods. However, for characterizing large-scale three-dimensional structures, oftentimes it is too expensive and thus impractical to conduct active seismic survey. Seismic imaging using passive sources has been used to image structures through the “pseudo-active” source imaging by assuming source information is known. However, in practice there exist some uncertainties on source information including location, origin time, source time function and radiation pattern, which can inevitably affect the final imaging result. In this study, we propose a new source-independent passive seismic imaging method based on reverse-time imaging with converted waves and a new imaging condition. This method uses the interference between P- and S-waves at conversion points for structure imaging by back-propagating seismograms recorded by all receivers. Since no forward modeling is needed in this method, source information is not needed.

Previously, we have applied the Generalized Radon Transform (GRT) method to use the scattered scattered P waves to image the San Andreas fault zone around Parkfield, California. Here we further extended the method to jointly use scattered P and SH waves. A hybrid imaging condition is applied to extract consistent structures from scattered P and SH images. In this way, more robust structure information can be determined from separate images with potential artifacts. We will compare imaging results from source-independent passive seismic reverse-time structure imaging method and “pseudo-active” GRT imaging method. Clear vertical reflectors are imaged on both sides of the SAF.

Presenting Author: Haijiang Zhang

Authors