【摘要】：利用云南2014年10月7日景谷6.6級、8月3日魯甸6.5級地震序列的波形與震相資料,消除區(qū)域地震波衰減與臺站場地響應后,計算得到2次地震序列的應力降。結果顯示,在研究所涉及的震級范圍內,應力降呈現隨震級增大而增大的趨勢。為盡可能消除震級對應力降的影響,對比了相同震級檔地震的應力降,結果顯示,景谷地震序列的平均應力降明顯高于魯甸地震,這可能與2次6.5級左右地震后震源區(qū)的應力狀態(tài)有關。從序列余震應力降的時、空變化對比來看,景谷6.6級地震后至2014年12月6日5.8、5.9級強余震發(fā)生前,應力降變化呈現先緩慢下降、進而轉折升高并持續(xù)高值的變化過程;同時,高應力降地震在空間上主要集中于5.8級強余震區(qū)域。這表明,主震發(fā)生后經過一個較短期的調整之后,5.8級強余震震源區(qū)的應力環(huán)境可能持續(xù)增強。5.8、5.9級強余震發(fā)生后,地震序列應力降快速下降至相對穩(wěn)定狀態(tài)。研究表明,2次6級左右強余震發(fā)生后,震源附近區(qū)域應力得到一定程度的釋放,應力環(huán)境降低,地震序列活動也趨于結束。對于后續(xù)沒有強余震發(fā)生的魯甸地震序列,余震應力降小于景谷地震序列相同震級檔地震的平均應力降,同時,主震后余震序列的應力降在時間上幾乎未發(fā)生太大的變化;結合主震能量釋放特點推測,震源區(qū)的應力在主震破裂過程中已得到較多的釋放,主震后震源區(qū)應力變化呈現逐漸恢復的過程,這可能是魯甸地震余震活動明顯較弱,后續(xù)亦未有較強余震發(fā)生的原因之一。
[Abstract]:Using the waveform and phase data of Yunnan Jinggu M = 6.6 earthquake sequence on October 7, 2014 and Ludian M = 6.5 earthquake sequence on August 3, 2014, the regional seismic wave attenuation and the site response of the station are eliminated, and the stress drop of the two earthquake sequences is calculated. The results show that the stress drop increases with the increase of magnitude. In order to eliminate the influence of magnitude on the stress drop as far as possible, the stress drop of the same magnitude earthquake is compared. The results show that the average stress drop of the Jinggu earthquake sequence is obviously higher than that of the Ludian earthquake. This may be related to the stress state in the focal area after two earthquakes with magnitude 6.5 or so. From the point of view of the stress drop of the sequence aftershocks, the variation of the stress drop after the Jinggu earthquake (M = 6.6) and before the aftershock with M = 5.890 M = 5.9 on December 6, 2014 shows a slow decrease, then a turning point and a continuous high value. The high stress drop earthquakes are mainly concentrated in the region of strong aftershocks with M = 5.8 in space. This indicates that after a relatively short period of adjustment after the occurrence of the main shock, the stress environment in the focal area of the strong aftershock with M = 5.8 may continue to strengthen. After the occurrence of the strong aftershock with M = 5.8 or M = 5.9, the stress drop of the earthquake sequence rapidly decreases to a relatively stable state. The results show that after two strong aftershocks with magnitude 6 or so, the regional stress near the earthquake source is released to a certain extent, the stress environment decreases, and the earthquake sequence activities tend to end. For the Ludian earthquake sequence with no strong aftershocks, the aftershock stress drop is smaller than the average stress drop of the same magnitude earthquake in Jinggu earthquake sequence, and the stress drop of the aftershock sequence after the main earthquake almost does not change much in time. Combined with the characteristics of the energy release of the main shock, it is inferred that the stress in the focal area has been released more during the rupture process of the main shock, and the stress variation in the focal area has gradually recovered after the main earthquake, which may be due to the obvious weakness of the aftershock activity of the Ludian earthquake. No strong aftershocks have occurred since then.
【作者單位】： 中國地震局地震預測研究所;中國地震臺網中心;
【基金】：中國地震局監(jiān)測預報司2016年度任務性科技專項(1640401320716)資助
【分類號】：P315

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