S Wave Velocity Structure Beneath Digital Seismic Stations of Yunnan Province Inferred from Teleseismic Receiver Function Modeling

Abstract

The S wave velocity structure within the depth of 0-100 km beneath digital seismic stations of Yunnan Province was obtained from teleseismic receiver function modeling. The results show that the crustal thickness changes greatly in Yunnan, reaching about 62 km in Zhongdian and Lijiang, and decreasing to 32-34 km in Jinghong, Simao and Changyuan in south. The thick crust extends from northwest to southeast, decreases in thickness and range, and is about 42 km thick around Tonghai. Its shape and range consist with Chuandian diamond block bounded by Xiaojiang and Yuanjiang faults. In the eastern and southern region, the crust is relatively thin, and the velocity contrast across Moho is obvious. In the areas with great variation of crustal thickness or thick crust area, the Moho is characterized by transition zone with high velocity gradient. In Yunnan region, S wave velocity structures show strong horizontal heterogeneity. Above the depth of 10 km, the S wave velocity in north area is obviously lower than that in south area, while within the depth of 10-20 km, the S wave velocity in north is higher than that in south. The velocity interface within crust is discontinuous, and the depth and range of lower velocity zones change with different seismic stations. There is no obvious crustal low velocity zone beneath nearly half of the stations. Influenced by the upper mantle in south area, within the depth of 40-50 km, S wave velocity in south area is higher than that in north, high velocity area extends to north, and the shape of low velocity zone tends to consist with Chuandian diamond block. The upper mantle velocity distribution within the depth of 70-80 km seems to be correlated to the distribution of strong earthquakes.

Tectonic controls on the late Miocene–Holocene volcanic eruptions of the Tengchong volcanic field along the southeastern margin of the Tibetan plateau

“…But at only »50 km deep to the west, it changes abruptly on the both sides of the Gaoligong mountains belt. Wu et al (2001) used receiver function to calculate the velocity structure of the Yunnan Province. Their results show that the thickness of the crust reduces gradually from northwest to southeast, whose shape and scale coincide with Sichuan-Yunnan relatively rigid blocks.…”

Crustal thickness and average Vp/Vs ratio variations in southwest Yunnan, China, from teleseismic receiver functions

“…The crustal structure is important to understand the dynamic process in this region. Relatively refined crustal structure in Yunnan is revealed by active source wide‐angle reflections profiles and teleseismic receiver functions analysis [ Hu et al , 2005; Langston , 1977b; Owens et al , 1984; J. Wu et al , 2001; Xu et al , 2006]. The crust thickness varies from ∼30 km at Simao to ∼60 km at Zhongdian, and the Moho dips toward the north generally [ Zhang and Wang , 2009].…”

Strong motion PGA prediction for southwestern China from small earthquake records

“…where R θφ is the radiation pattern of the shear excitation, with the assumption that the energy was equally partitioned into two horizontal components, R θφ = 0.6; F is the free surface effect, F = 2.0; V is the vectorial partitioning of shear-wave energy into two components of equal amplitude, (McGuire and Hanks, 1980); R 0 is a reference distance, R 0 = 1 km (Boore, 2003); ρ s is the density in the vicinity of the source, ρ s = 2.8 g cm −3 ; β s is the shear-wave velocity in the vicinity of the source, β s = 3.5 km s −1 (Wu et al, 2001;Xie et al, 2012).…”