マスターイベント法による近畿地方北部における微小地震の震源の精密決定と深さ分布

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  • 伊藤 潔
    京都大学理学部付属地震予知観測地域センター
  • 黒磯 章夫
    京都大学理学部付属地震予知観測地域センター

書誌事項

タイトル別名
  • Precise Determination of Hypocenters by Master Event Method and the Distribution of Focal Depths for Microearthquakes in Northern Kinki District, Japan
  • マスターイベントホウ ニ ヨル キンキ チホウ ホクブ ニ オケル ビショウ

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抄録

Accuracy of master event location method is studied for the microearthquakes recorded by the telemetered network of the Abuyama Seismological Observatory in northern Kinki district, Japan. The range in which the master event method is effective is examined in order to apply the master event technique using several master events to earthquakes in large area. Moreover the variations of hypocenters are estimated for the variations of the velocity and that of the thickness of the surface layer and the velocity of basement layer.<br>The master event method is effective for the events of which epicenters are within 20km from a master event, in the case the error of relative location is 0.2km for epicenters and 0.5km for focal depths. The errors of the relative epicenters and focal depths are also small for the possible change of structure parameters. Therefore, the regional change of focal depths can be detected clearly by the master event method using several master events. The precise distribution of hypocenters determined by the use of six master events shows that focal depths of all the earthquakes in this district are located in upper part of the crust shallower than 20km. Moreover the depth-frequency distribution of the earthquakes indicates two peaks at depths of 7-9 and 11-13km with abrupt decrease at 15-20km. Furthermore the depth of the seismic-aseismic boundary changes from place to place, such that the boundary dips from southwest to northeast by about 5km. The focal depths determined by this method is accurate enough to discuss the regional variation of seismic-aseismic boundary and its relation to the brittle-ductile boundary in the crust and to the Conrad discontinuity.

収録刊行物

  • 地震　第２輯

    地震　第２輯 41 (2), 179-188, 1988

    公益社団法人 日本地震学会

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