V p and V p/V s structures in the crust and upper mantle of the Taiwan region, China

Abstract

A tomographic study of the V p and V p /V s structures in the crust and upper mantle beneath the Taiwan region of China is conducted by simultaneous inversion of P and S arrival times. Compared with the previous tomographic results, the spherical finite difference technique is suitable for the strong heterogeneous velocity structure, and may improve the accuracy in the travel time and three-dimensional ray tracing calculations. The V p and V p /V s structures derived from joint inversion and the relocated earthquakes can provide better constraints for analyzing the lateral heterogeneity and deep tectonic characters in the crust and upper mantle. Our tomographic results reveal significant relations between the seismic wavespeed structure and the tectonic characters. In the shallow depth, sedimentary basins and orogen show distinct wavespeed anomalies, with low V p , high V p /V s in basins and high V p , low V p /V s in orogen. As the suture zone of Eurasian Plate and Philippine Sea Plate, Longitudinal Valley is characterized by a significant high V p /V s anomaly extending to the middle-lower crust and upper mantle, which reflects the impact of rock cracking, partial melting, and the presence of fluids. In the northeast Taiwan, the V p , V p /V s anomalies and relocated earthquakes depict the subducting Philippine Sea Plate under the Eurasian Plate. The high V p of oceanic plate and the low V p , high V p /V s atop the subducted oceanic plate extend to 80 km depth. Along the east-west profiles, the thickness of crust reaches 60 km at the east of Central Range with eastward dipping trend, which reveals the eastward subduction of the thickened and deformed crust of the Eurasian continental plate.Taiwan region, P wave velocity, V p /V s ratio, lithosphere structure, tomography

Strong plasmonic fluorescence enhancement of individual plant light-harvesting complexes

“…On the one hand, amplification of the local electric field induced by the localized surface plasmon resonance (LSPR) of metallic NPs results in significantly enhanced excitation rate of the pigments. On the other hand, the presence of metallic NPs manipulates the local density of optical states of the nearby pigments, thereby enhancing the radiative rates (the Purcell effect), which in turn leads to a change in the fluorescence lifetime and QY of the pigments 20,33 . In general, PFE depends on several factors, including nanoparticle shape, size, position and orientation of the pigment with respect to a metallic nanoparticle.…”

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An efficient and adaptive approach for modeling gravity effects in spherical coordinates

“…The correlation coefficient reaches 0.70, and the gravity residuals for most observation points are less than 20 mGal. Small scale gravity residuals may relate to the shallow small scale structures, so that the coarse grid spacing of the tomographic model (~10 km laterally and 4-16 km vertically) can't compensate these gravity anomalies (Li et al, 2009b). Compared with synthetic gravity anomalies of the model from arrival time inversion only, the pattern has significant discrepancies and the correlation coefficient is as low as 0.23.…”

“…One model is from the individual inversion of P-and S-wave arrival time only (Li et al, 2009b), and another one is the preliminary result from the joint inversion of arrival time and gravity data by the method proposed by Roecker et al (2004). The spherical finite difference technique is used to implement the 3-D ray tracing (Li et al, 2009a).…”

“…The spherical finite difference technique is used to implement the 3-D ray tracing (Li et al, 2009a). The P and S arrival times are from the seismic station networks in the Taiwan region during 1992-2004, which consists of about 135,000 P and 77,000 S arrivals from nearly 6000 events at 92 stations (Li et al, 2009b). For the joint inversion, the arrival time and gravity data are involved in the inversion simultaneously.…”