Velocity Structure, Seismicity, and Fault Structure in the Peikang High Area of Western Taiwan

Abstract

As an attempt to investigate the sub-surface geometry of the Peikang High, and the structural fe atures that may have influenced the regional seismicity of western Taiwan, a three-dimensional (3-D) P-wave velocity model has been developed. The velocity model was determined by simulta neously inverting of P-and S-wave arrival times recorded by the Central Weather Bureau Seismographic Network for earthquakes occurred from 1991 to 2000. In order to have a good constrain for the shallow part of the velocity model, the results of geophysical survey and drilling data of the Peikang High region conducted by the Chinese Petroleum Corporation are used in the initial 3-D model. Based on the results of restoring resolution and checkerboard test, the upper and middle crust is well resolved through out the onshore and southern part of offshore in the study area. In general, the velocity transition zone from low to high is located beneath the Western Foothills region. The prominent feature of the velocity model is that the uplift high velocity volume exist in the middle-and lower-crust beneath the areas west to the Western Foothills should be associated with the Peikang High. The Peikang High is overlaid with the Coastal Plain, a basin type containing low velocity materials. The geometry of the Peikang High mate rials seems to affect the distribution of surficial faults and topography. In addition, most of the relocated Chi-Chi hypocenters are in the low velocity zones of the study area.

How the structural architecture of the Eurasian continental margin affects the structure, seismicity, and topography of the south central Taiwan fold‐and‐thrust belt

“…The most important along‐strike change in the south central Taiwan fold‐and‐thrust belt takes place at zone A, which is the on‐land prolongation of the upper part of the necking zone (Figures , and ). Zone A forms the southern flank of Peikang Basement High, which has been widely recognized as an area of significant change in the structure, fault kinematics, and seismicity of the thrust belt [e.g., Lu et al ., ; Deffontaines et al ., ; Lacombe et al ., ; Mouthereau et al ., ; Cheng et al ., ; Mouthereau and Lacombe , ; Wu et al ., , ; Byrne et al ., ; Alvarez‐Marron et al ., ]. It has been suggested that these along‐strike changes are largely due to buttressing [ Hayward and Graham , ] of the thrust system by the basement high [e.g., Lu et al ., ; Lacombe et al ., ].…”

Structural complexities in a foreland thrust belt inherited from the shelf-slope transition: Insights from the Alishan area of Taiwan

“…Many of the structural and stratigraphic changes that we outline above have been attributed to the Alishan area being located along the southern flank of the Peikang High [e.g., Mouthereau et al , ; Cheng et al , ; Wu et al , ; Byrne et al , ], which comprises a number of approximately east‐northeast trending extensional faults in the footwall to the exposed thrust system. Many of these are buried beneath synorogenic sediments but have been either imaged in reflection seismic data or sampled in boreholes [ Yang et al , ; Chen and Yang , ; Lin et al , ].…”

Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills

“…The reentrant in the range front observed at the latitude of the Choushui river might be such a feature due to indention by the Peikang High (Figures 2 and 11). This morphological signature is clearly defined, and appears slightly further north than the inferred east‐west present position of this margin horst [e.g., Cheng et al , 2003; Hsu and Sibuet , 1995; Lin et al , 2003] (Figure 2). Transfer faulting, consistent with indentation tectonics, has been described in the area [ Mouthereau et al , 1999].…”

“…The Chinese margin shows lateral complexities due to basins and horsts formed during a phase of extension prior to the current collisional regime [e.g., Lin et al , 2003; Teng et al , 1991]. One of these structures, the Peikang High offshore west central Taiwan [e.g., Cheng et al , 2003; Hsu and Sibuet , 1995; Lin et al , 2003], is believed to be responsible for the arcuate geometry of the range front in this region [ Mouthereau et al , 1999] (Figure 2). …”