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Cutoff depth of seismicity and thermal structure in the Hokuriku and Hida regions.

北陆和飞騨地区地震活动和热结构的截止深度。

基本信息

批准号：
04640402
负责人：
ITO Kiyoshi
金额：
$ 0.83万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640402/
关键词：
Distribution of earthquake Cutoff depth of seismicity Focal depth of earthquake Large inland earthquake Strength of the crust Seismicity Surface heat hlow Thermal structure 地殻強度

项目摘要

P and S wave data of seismological observations have been collected to obtain precise hypocenters, especcially focal depths for the earthquakes in the Hokuriku and Hida regions, northern central Honshu, Japan. The data have been recorded by the microearthquake observatories of the Disaster Prevention Research Insatitute, Kyoto University during the period from 1978 to 1993, since the telemetered system was installed at the observatories. Durihg the period more than 25,000 earthquakes were located by the routine networks. All P and S wave data as well as amplitude and total duration times (F-P) were collected and aranged in a same format for convinience of analyzes.In this study, all earthquakes were relocated using the data, adding those obtained by temporary observations. Precise travel times of P and S waves, or crustal structures are necessary to obtain accurate hypocenters. Therefore, travel times or crustral structures derived from explosion seismic observations were also collected and reanalyzed. In the regions at the surface layr with P-wave velocity less than 6 km/s is about 1km and very thin, underlained by 5.8-6.0km/s layr with a thickness of about 13km. By using this structure all earthquakes were relocated and accurate ones were selected to study the relationship between focal depths and thermal structure. Data of heat low and thermal gragient were also collected to compare them with the cutoff depths. In consequence, the cutoff depths of events along the Atotsugawa fault are rather deep as 12-15km, while those under the Hida mountains, whehe some active volcanoes exist and heat flow is high, are shallow as about 5-8km. Besides under the Yake-dake volcano, which is the most active volcano in the Hida mountains, focal depths are as shallow as 3km. Thus, Cutoff depth of seismicity in the Hokuriku and Hida regions are closely related to the thermal structure.

收集地震观测的纵波和横波数据，以获得精确的震源，特别是日本本州中北部北陆和飞騨地区地震的震源深度。这些数据是京都大学防灾研究所微地震观测站安装遥测系统以来，从1978年至1993年期间记录的数据。在此期间，常规网络定位了超过 25,000 次地震。为了便于分析，所有纵波和横波数据以及振幅和总持续时间（F-P）均以相同的格式收集和排列。在本研究中，所有地震都使用这些数据进行了重新定位，添加了临时观测获得的数据。要获得准确的震源，需要精确的纵波和横波或地壳结构的传播时间。因此，还收集并重新分析了爆炸地震观测得出的走时或地壳结构。表层纵波速度小于6km/s的层厚约1km，很薄，下面有5.8-6.0km/s的层，厚约13km。通过使用该结构，对所有地震进行了重新定位，并选择了准确的地震来研究震源深度与热结构之间的关系。还收集了低热量和热梯度数据，以将它们与截止深度进行比较。因此，原子津川断层沿线的事件截止深度相当深，为12-15公里，而飞驒山脉下方存在一些活火山且热流较高，事件的截止深度较浅，约为5-8公里。除了飞驒山脉最活跃的火山烧岳火山下方外，震源深度浅至3公里。由此可见，北陆和飞騨地区地震活动的截止深度与热结构密切相关。