库尔勒5.8级和库车6.0级地震地方震尾波持续时间比的初步研究

A PRELIMINARY STUDY ON THE DURATION RATIO OF THE CODA WAVE OF LOCAL EARTHQUAKES FOR THE KUERLE 5.8 AND KUCHE 6.0 MAGNITUDE EARTHQUAKES

摘要:

选用地方震尾波长度两水平分量的算术平均值与垂直分量之比τ_H/τ_v作为参量,分析处理了库尔勒1978年4月22日5.8级地震前后库尔勒地震台65型地震仪所记录的104个地方震,以及库车1979半3月29日6.0级地震前后新源地震台维开克型地震仪所记录的128个地方震。取地震前几分钟噪声水平的两倍(毫米数)作为噪声带确定尾波的结止时间。所取地方震震中距Δ小于200公里,震级区间取0.7≤M_L≤4.5。结果表明,在库尔勒5.8级地震前一个多月库尔勒台的τ_H/τ_V出现了一定的低值变化,而在库车6.0级地震前利用新源台求出的τ_H/τ_V变化不太明显,略有异常显示。

Abstract:

The ratio between the arithmetic average of two horizontal lomponents and the vertical component of the seismic coda length of local earthquakes is selected as the parameter. We have analysed the seismograms of the 104 local earthquakes occurred before and after 5.8 magnitude main shock on April 22, 1978(during Jan. 1, 1977……Aug. 8, 1978), recorded by 65 type seismograph at Kuerle seismological station, and those of the 128 local earthquakes occurred before and after Kuche 6.0 magnitude main shock on March 29, 1979(during Feb. 1, 1977……June 6, 1979), recorded by BTK type seismograph at Xinyuan seismological station. The duplex maximum noise amplitude(mm)in a few minutes before P wave first motion is selected as the noise belt to determine the ending time of coda wave. The epicentral distance of local earthquakes is △<200 km, magnitude interval is 0.7≤M_s≤4.5. The result shows that a certain low value of τ_H/τ_V at Kuerle seismological station occurred about a month before the Kuerle 5.8 magnitude earthquake while the change of τ_H/τ_V recorded by Xinyuan seismological station, was not so obvious before the Kuche 6.0 magnitude earthquake, although some abnormal display occurred.