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タイトル: 微小地震観測網による遠地地震P波の波形データ処理方式について
その他のタイトル: Data Processings of Teleseismic P Waves recorded by Microearthquake Observation Networks
著者: 荘, 燦濤
溝上, 恵
著者(別言語): Zhuang, Can Tao
Mizoue, Megumi
発行日: 1982年3月31日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第56冊第4号, 1982.3.31, pp. 653-673
抄録: Seismic signals recorded by microearthquake observation networks are available for a hypocentral determination of local events as well as for an evaluation of the azimuth and apparent velocity of the teleseismic P waves. The coherent nature of teleseismic P waves recorded at each of the stations of a microearthquake observation network satisfies a basic requirement for the application of an array processing. In the case of the Wakayama Microearthquake Obseravatory with a network spanning 120-150 km, the coherency function is as large as 0.8-0.9 in the frequency range of less than 2.5 Hz in which the power spectrum amplitude has a maximum peak. The cross-correlation function is used for the arrival time measurement of P waves relative to each of two specified stations. The damped least squares method is introduced to evaluate the azimuth and apparent velocity of incoming teleseismic P waves. The standard error in the azimuth is less than ±1° and that of the apparent velocity is less than 0.016 relative to its value, when the arrival time difference of the P waves between the two stations can be measured with the error of less than 0.1 sec. Despite of the coherent nature of teleseismic P waves recorded by a microearthquake observation network, a nonsystematic distribution of stations in geometry produces unfavourable effects on the resolution of the data processing. In the case of ordinary array stations, the main lobe of the beam pattern is predominant in its amplitude and is clearly separated from side lobes through the delay and sum procedures. In the case of microearthquake observation networks, however, the simple delay and sum procedure fails to make an evident separation of the main lobe in the beam pattern. The calculation of the integrated pattern in the frequency domain is found to be a pracitical method for the enhancement of the main lobe when a microearthquake observation network is used for the measurements of the azimuth and the apparent-velocity of teleseismic P waves.
URI: http://hdl.handle.net/2261/12825
ISSN: 00408972


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