Two-month continuous waveforms of 108 broadband seismic stations in Fujian Province and its adjacent areas are used to compute noise cross-correlation function(NCF). The signal quality of NCF is improved via the appli...Two-month continuous waveforms of 108 broadband seismic stations in Fujian Province and its adjacent areas are used to compute noise cross-correlation function(NCF). The signal quality of NCF is improved via the application of time-frequency phase weighted stacking. The Rayleigh and Love waves group velocities between 1 s-20 s are measured on the symmetrical component of the NCF with the multiple filter method. More than 5,000 Rayleigh wave dispersion curves and about 4,000 Love wave dispersion curves are obtained and used to invert for group velocity maps. This data set provides about 50 km resolution that is demonstrated with checkerboard tests. Considering the off great circle effect in inhomogeneous medium, the ray path is traced based on the travel time field computed with a finite difference method. The inverted group velocity maps show good correlation with the geological features in the upper and middle crust. The Fuzhou basin and Zhangzhou basin showed low velocity on the short period group velocity maps. On the long period group velocity maps, the low velocity anomaly in the high heat flow region near Zhangzhou and clear velocity contrast across the Zhenghe-Dapu faults, which suggests that the Zhenghe-Dapu fault might be a deep fault.展开更多
The Longhai-Zhangpu coastal region lies in the so-called Golden Triangle area of southern Fujian Province. Tectonically, it is located on the southern segment of the Changle-Zhao＇an fault zone, being one of the regio...The Longhai-Zhangpu coastal region lies in the so-called Golden Triangle area of southern Fujian Province. Tectonically, it is located on the southern segment of the Changle-Zhao＇an fault zone, being one of the regions of Tertiary and Quaternary basaltic eruptions in China＇s southeast coastal area. In this area there are the Liuhui （Longhai County ）-Jiangjun＇ ao （Zhangpu County） and Gangwei （ Longhai County ）-Huxi （ Zhangpu County ） faults, along which basaltic eruption has occurred. The faults have been significantly active since the Quaternary, and several small to moderate earthquakes have occurred on the faults. In this paper, the basic characteristics of the late Quaternary activities and the combination relation of the faults are discussed on the basis of an analysis of along-fault basaltic eruptions during the late Tertiary to late Pleistocene, as well as the differential variation of geomorphic surfaces and marine deposits on both sides of the faults. The results show that the Liuhui-Jiangjun＇ao fault is a late Pleistocene active fault. During the late Tertiary to late Pleistocene, three stages of basaltic eruptions occurred along the fault, among which the first stage occurred in the Pleistocene to early Pleistocene, the second stage in the middle Pleistocene and the third stage in the late Pleistocene. The Gangewei-Huxi fault can also be considered a late Pleistocene active fault. The elevation rate of the downthrown side of the fault is estimated to be 1. 11mm/a.These two faults have dissected the area into the Gangwei graben, south Taiwushan horst and the graben in the sea area to the east of Liuhul-Jiangjun＇ao.展开更多
基金sponsored by the Youth Foundation of Fujian Earthquake Agency(Y201710)the Basic Research Fund of the Institute of Earthquake Forecasting,China Earthquake Administration(2015IES010302)
文摘Two-month continuous waveforms of 108 broadband seismic stations in Fujian Province and its adjacent areas are used to compute noise cross-correlation function(NCF). The signal quality of NCF is improved via the application of time-frequency phase weighted stacking. The Rayleigh and Love waves group velocities between 1 s-20 s are measured on the symmetrical component of the NCF with the multiple filter method. More than 5,000 Rayleigh wave dispersion curves and about 4,000 Love wave dispersion curves are obtained and used to invert for group velocity maps. This data set provides about 50 km resolution that is demonstrated with checkerboard tests. Considering the off great circle effect in inhomogeneous medium, the ray path is traced based on the travel time field computed with a finite difference method. The inverted group velocity maps show good correlation with the geological features in the upper and middle crust. The Fuzhou basin and Zhangzhou basin showed low velocity on the short period group velocity maps. On the long period group velocity maps, the low velocity anomaly in the high heat flow region near Zhangzhou and clear velocity contrast across the Zhenghe-Dapu faults, which suggests that the Zhenghe-Dapu fault might be a deep fault.
文摘The Longhai-Zhangpu coastal region lies in the so-called Golden Triangle area of southern Fujian Province. Tectonically, it is located on the southern segment of the Changle-Zhao＇an fault zone, being one of the regions of Tertiary and Quaternary basaltic eruptions in China＇s southeast coastal area. In this area there are the Liuhui （Longhai County ）-Jiangjun＇ ao （Zhangpu County） and Gangwei （ Longhai County ）-Huxi （ Zhangpu County ） faults, along which basaltic eruption has occurred. The faults have been significantly active since the Quaternary, and several small to moderate earthquakes have occurred on the faults. In this paper, the basic characteristics of the late Quaternary activities and the combination relation of the faults are discussed on the basis of an analysis of along-fault basaltic eruptions during the late Tertiary to late Pleistocene, as well as the differential variation of geomorphic surfaces and marine deposits on both sides of the faults. The results show that the Liuhui-Jiangjun＇ao fault is a late Pleistocene active fault. During the late Tertiary to late Pleistocene, three stages of basaltic eruptions occurred along the fault, among which the first stage occurred in the Pleistocene to early Pleistocene, the second stage in the middle Pleistocene and the third stage in the late Pleistocene. The Gangewei-Huxi fault can also be considered a late Pleistocene active fault. The elevation rate of the downthrown side of the fault is estimated to be 1. 11mm/a.These two faults have dissected the area into the Gangwei graben, south Taiwushan horst and the graben in the sea area to the east of Liuhul-Jiangjun＇ao.
