Fingerprint Identification Using Noise in the Horizontal-to-Vertical Spectral Ratio: Retrieving the Impedance Contrast Structure for the Almaty Basin (Kazakhstan)

Session: Near-Surface Effects: Advances in Site Response Estimation and Its Applications [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Detailed knowledge of the three-dimensional (3D) structure of basins underlying urban areas is of major importance for improving the assessment of seismic hazard and risk. However, mapping the major features of the associated shallow geological layers becomes expensive in terms of required resources when large areas need to be covered. In this study, we propose an innovative tool, based mainly on single station noise recordings and the horizontal-to-vertical spectral ratio (H/V), to identify and locate the depth of major seismic impedance contrasts. The method is based on the identification of so-called fingerprints of the major impedance discontinuities and their migration to depth by means of an analytical procedure. The capability of the procedure to retrieve the main impedance contrasts at depth was tested by using numerical simulations based on a semi-analytical method that uses an improved Thompson-Haskell propagator matrix algorithm. The method was applied to seismic noise recordings collected in the city of Almaty (Kazakhstan), which has suffered from significant earthquake damage during the past 130 years. The estimated impedance contrasts versus depth profiles were interpolated in order to derive a 3D model, which after calibration with available borehole data allowed the major tectonic features in the subsurface to be identified. Such 3D reconstructions could therefore be employed for numerical simulations of ground motion and the preparation of accurate earthquake impact scenarios as part of earthquake risk mitigation efforts.

Presenting Author: Stefano Parolai

Authors