South Ilan plain high-resolution 3-D S-wave velocity from ambient noise tomography

Kai Xun Chen, Po Fei Chen, Li Wei Chen, Huajian Yao, Hongjian Fang, Po Li Su

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The Ilan Plain in northeastern Taiwan is located at a pivotal point where the Ryukyu trench subduction zone, the northern Taiwan crustal stretching zone, and the ongoing arc-continent collision zone converge. In contrast to the North Ilan Plain, the South Ilan Plain exhibits a thin unconsolidated sedimentary layer with depths ranging from 0-1 km, high on-land seismicity and significant SE movements relative to Penghu island. We deployed a dense network of 43 short-period vertical component Texan instruments from June to November 2013 in this study, covering most of the South Ilan Plain and its vicinity. We then used the ambient noise tomography method for simultaneous phase and group Rayleigh wave velocity measurements to invert a high-resolution 3-D S-wave for shallow structures (up to a depth of 2.5 km) in the South Ilan Plain. We used the fast marching method for ray tracing to deal with ray bending in an inhomogeneous medium. The resulting rays gradually bend toward high velocity zones with increasing number of iterations. The high velocity zone results are modified by more iterations and the resolutions become higher because ray crossings are proportional to ray densities for evenly distributed stations. The final results agreed well with known sedimentary basement thickness patterns. We observed nearly EW trending fast anomalies beneath the mountainous terrain abutting to the South Ilan Plain. The Chingshui location consistently exhibited a low S-wave velocity zone to a depth of 1.5 km.

Original languageEnglish
Pages (from-to)375-385
Number of pages11
JournalTerrestrial, Atmospheric and Oceanic Sciences
Volume27
Issue number3
DOIs
StatePublished - Jun 2016

Keywords

  • Ambient noise tomography
  • Dense Texan array
  • The South Ilan Plain

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