Crustal Structure of the Northeastern Taiwan Area From Seismic Refraction Data and Its Tectonic Implications

Abstract

Seismic refraction data from onshore and offshore experiments in the eastern-northeastern Taiwan region \\'ere used to study the velocity struc ture by the two-dimensional ray-t . racing method. In the \1elocity model, a structural fault boundary located beneath the Longitudinal Valley "ras used to separate the northern Coastal Range (CR) on the eastern side from the eastern flank of the Central Range (EFCR) on the western side. The P 'vave 'relocities from the surface to the dept .h of 12-15 km varied from 3.9 to 5.8 km/s beneath the CR and from 4.8 to 6.1 km/s beneath the EFCR. Com paring the velocity structures along various latitudes, it \\'as found that the CR extends northward to 24.2 <> N. The velocity structures of the CR, the Hsinchen Ridge (HR) and the Yaeyama Ridge (YR) indicate that the HR and the YR both belong to t . he same type of tectonic unit as the CR. To the north of 24.2 <• N, the velocit)' structure of the Ilan Ridge (IR), located be t,veen the EFCR and the southwest . ern end of the Ryukyu arc, is similar to that . of the EFCR; hence, probably indicating it is the northeastern exten sion of the EFCR. This suggests that the EFCR bends eastward and be longs to the same tectonic unit as the southwestern Ryukyu arc. From a comparison of the velocity structures of the CR, EFCR and of other typical continental arcs, orogens and oceanic arcs in the literature, it can be con cluded that the northern CR b�longs to an oceanic arc and that the EFCR is a continental arc. Further more, from the analysis of the velocity struc tures beneath the CR and EFCR, it is believed that the upper crust of the CR is weaker in strength than the EFCR, which means that the arc-conti nent collision is not an appropriate model for the formation of Tai\\ran is land.

The application of large volume airgun sources to the onshore-offshore seismic surveys: implication of the experimental results in northern South China Sea

“…In contrast, the two portable seismic stations along the extension of the shooting line can record the airgun signals of more than 100 km. Similar situation is also seen in the TAICRUST experiment of Taiwan, where the farthest signals recorded by permanent seismic stations are 80 km in southern Taiwan [19,20] , and only 40 km in northeast Taiwan [21] . There were many permanent seismic stations on Taiwan Island but only a few of them recorded the airgun signals at short distances.…”

Transition from oblique subduction to collision in the northern Luzon arc‐Taiwan region: Constraints from bathymetry and seismic observations

“…In the region of this study the transition from subduction along the Manila trench to collision in Taiwan occurs south of Taiwan. Although abundant evidence argues that the Coastal range located to the east of the LV probably shares the same origin as the Luzon arc [e.g., Chi et al, 1981;Barrier and Angellet, 1986;Cheng et al, 1996;Shyu et al, 1996;Lundberg et al, 1997], it seems difficult to directly connect the present-day plate suture in the eastern Taiwan (i.e., the LV) to the plate boundary along the Manila trench. Lin and Tsai [1981 ] proposed a transform fault across the southern Taiwan connecting the two structures.…”

Lithospheric Structure of Philippine Sea Plate near the Western End of Ryukyu Subduction Zone and Some of its Tectonic Effects

“…2, the Coastal Range (province v) in eastern Taiwan plays an important role in the arc continent collision model (e.g., Barrier and Angelier 1983). It is believed that Coastal Range is a part of both the Luzon arc, and the uplifted part of the forearc basin (e.g., Cheng et al 1996Cheng et al , 1998, which has formed from the eastward subduction of the South China Sea lithosphere beneath the Philippine Sea plate along the Manila trench. In the arc-continent collision model, the Luzon arc has been colliding with the Eurasian plate, resulting in the growth of the western foothills and Central Range of Taiwan through deformation of strata and basement rocks of the Asian continental margin.…”

“…Based on the P-wave velocity structure derived from seismic refraction experiments in the northeastern Taiwan area, Cheng et al (1996) found that the eastern flank of the Central Range in central Taiwan (designated by EFCR in Fig. 2) and the western end of the Ryukyu arc have similar characteristics in seismic velocity and speculated that they are parts of the same tectonic unit.…”

“…Structural provinces on the Taiwan island (Ho 1986(Ho , 1988 and its sur rounding offshore region. The two belts on the map are Ryukyu arc and Luzon arc newly defined by Cheng et al (1996) and Shyu et al (1996). The bathymetric data are from Liu et al (1996Liu et al ( , 1998 1995), the Luzon arc has been colliding with the Ryukyu arc, lying on the edge of the Eurasian plate.…”