Significant contribution of the shallow crust to seismic PKP travel-time residuals and implications: An example from Taiwan and nearby islands
Journal
Journal of Asian Earth Sciences
Journal Volume
46
Pages
86-91
Date Issued
2012
Author(s)
Abstract
Array observations indicate that the relative PKP travel-time residuals in the Taiwan region vary from -2.5 to. +2.0. s, a range greater than the largest known teleseismic travel-time residuals from deep Earth. PKP waves are generally employed to probe structures of the deep Earth; however, the contribution of shallow geological structures to PKP waves is generally undefined and the implications of such a contribution have rarely been discussed. Current travel-time tomographic models of Taiwan are able to predict less than 40% of the observed PKP residuals, and the PKP residuals are consistent with the pattern of station corrections used in determining local earthquakes. Detailed island-wide gravity measurements indicate that the distribution of Bouguer anomalies, which were previously proposed to be induced by thick sedimentary deposits in large tectonic basins, is consistent with the pattern of PKP travel-time residuals. In conclusion, the observed PKP residuals are strongly affected by shallow sediments. Therefore, the contribution of residuals from shallow crustal structures should be carefully considered when employing PKP observations for imaging structures of the deep Earth or the deep crust and upper mantle. © 2011 Elsevier Ltd.
Subjects
arrival time; Bouguer anomaly; correlation; crustal structure; crustal thickness; P-wave; seismic data; seismic tomography; structural geology; teleseismic wave; travel time; upper mantle; wave generation; Taiwan
Type
journal article