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
Seismicity in northern Arizona is concentrated in a northwest-southeast trending belt that stretches from the Utah border south to the edge of the Colorado Plateau. Located within this NASB （Northern Arizona Seismic ...Seismicity in northern Arizona is concentrated in a northwest-southeast trending belt that stretches from the Utah border south to the edge of the Colorado Plateau. Located within this NASB （Northern Arizona Seismic Belt） is the San Francisco volcanic field, classified by the United States Geological Survey as potentially active. The last volcanic event in the field was located at Sunset Crater and occurred less than 1,000 years ago. Eruption intervals in the volcanic field are of the same order of length of time. Seismic monitoring of the volcanic field area has improved greatly since 1985 with the establishment of new network seismic stations. This has allowed for a lowered threshold of detection of seismic events and improved location capabilities. As an example of the result of this improved ability to locate smaller tremors, two swarms have been identified in the field, the 2009 Halloween swarm near Sunset Crater volcano and the 2011 swarm near Flagstaff, the largest urban community in northern Arizona.展开更多
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.
文摘Seismicity in northern Arizona is concentrated in a northwest-southeast trending belt that stretches from the Utah border south to the edge of the Colorado Plateau. Located within this NASB （Northern Arizona Seismic Belt） is the San Francisco volcanic field, classified by the United States Geological Survey as potentially active. The last volcanic event in the field was located at Sunset Crater and occurred less than 1,000 years ago. Eruption intervals in the volcanic field are of the same order of length of time. Seismic monitoring of the volcanic field area has improved greatly since 1985 with the establishment of new network seismic stations. This has allowed for a lowered threshold of detection of seismic events and improved location capabilities. As an example of the result of this improved ability to locate smaller tremors, two swarms have been identified in the field, the 2009 Halloween swarm near Sunset Crater volcano and the 2011 swarm near Flagstaff, the largest urban community in northern Arizona.
