Sedimentary structure of the western Bohai Bay basin and other basins in North China revealed by frequency dependent P-wave particle motion

Abstract

High-resolution seismic models of sediment basins are critical inputs for earthquake ground motion prediction and petroleum resource exploration. In this study we employed a newly developed technique that utilizes the frequency-dependent nonlinear P-wave particle motion to estimate sedimentary structure beneath the Bohai Bay basin. A recent study suggests that the delay of the P wave on the horizontal component relative the vertical component and its variations over frequency are caused by interference of the direct P wave with waves generated at the sediment base. The frequency-dependent delay time can be used to constrain sediment thickness and seismic velocity beneath recording stations. We measured the particle motions of teleseismic P waves recorded by 249 broadband stations of the North China Array, which covers the western Bohai Bay basin and its surrounding areas. We found that the P waves of 90 stations inside the Bohai Bay basin and other local basins within the Taihang and Yanshan mountain ranges exhibit significant frequency-dependent nonlinear particle motions, and used the particle motion data to invert the sediment thickness (Z0) and surface S-wave velocity (β0). The estimated sediment thickness inside the Bohai Bay Basin varies from 1.02 km to 3.72 km, with an average of 3.20 km, which roughly agrees with previous active source studies.