Finite Element Reverse Time Imaging for Earthquake Sources and Scatterers

彈性波源及散射體的逆時影像重建

黃柏壽(Bor-Shouh Huang) ； 葉永田(Yeong Tein Yeh)

《Terrestrial, Atmospheric and Oceanic Sciences》 2卷1期 (1991/03) Pp. 17-33

摘要

本文應用波動方程式的可逆性討論彈性波的逆時影像重建。依據逆時傳播的觀念以評估重建彈性波源及散射體影像的可行性。本文採用有限元素法計算彈性波在介質中的傳播。相同的計算機程式並用以推求空間逆時影像。經由適當的消除人爲邊界反射，在只利用地表的曆時記錄即有效的推求出震源及散射體的精確立置。本文結果顯示單一點震源，有限長斷層錯動及多重點震源皆可有效的加以重建。即使利用含有非常明顯直接波信號的歷時記錄亦可有效的重建地下散射體的影像。採用有限元素法計算逆時影像重建的技術經證實是可行且易於應用於其他的研究領域。

並列摘要

In this study, we applied the reversibility of elastic wave to a discussion of the reverse time propagation of wave equation. Based on the backward propagation concept, we evaluated the feasibility of reconstructing the image of elastic wave sources and scatterers. The finite element method was used to calculate elastic wave propagation in the medium. The same computational code was also used to reconstruct the reverse time image. It was found that after our careful processing of the absorption boundary for artificial reflection, we could use the time-trace records at the surface to invert the locations of seismic sources or underground scatterer accurately. Our results show that point source, finite fault and multi-sources are well reconstructed. Although direct waves are much stronger than scattering wavefields, the imaging of the underground anomaly is still well reconstructed from the reverse time process. The image reconstruction technique based on the finite element method is flexible and easily to use for many applications.