1988年云南澜沧-耿马7.6级地震前热力场的研究(英文)  

THE STUDY OF THE THERMAL STRESS FIELD BEFORE THE EARTHQUAKE(Ms 76)AT LANCANG-GENGMA,YUNNAN IN 1988

作　　者：黄永祥[1] 黄浩雄[1] 

机构地区：[1]云南省地震局

出　　处：《地震研究》1998年第2期196-204,共9页Journal of Seismological Research

摘　　要：本文根据云南深井精密地温观测网的实测值，求得震前（１９８８年１０月１日—２８日）短临变温场；参照张之立热应力模型解析法，同时采用热应力差分有限元法；详细计算与展示了震前热应力场与本次地震的关系。经研究表明：（１）该次地震前出现了强烈的热异常，其最大热异常梯度带就位于未来强震区（澜沧—耿马）附近；最大热异常时段出现于临震前（１９８８年１０月１日—２８日）。最大热异常梯度带的变温值—浅层（２００ｍ左右深处的实例值）为０６℃，中层（推至２ｋｍ深处）为１３℃，深层（推至８—１３ｋｍ震源附近）为５０℃左右。（２）震前出现的最大热异常梯度带也就是最大热应力集中带—未来强震区澜沧—耿马附附近。该区最大热力应力值—浅层（２００ｍ左右近地表）为１ＭＰａ左右，中层（２ｋｍ左右）为１３—１８ＭＰａ，深层（震源区附近）为５９—１１３ＭＰａ。（３）８—１３ｋｍ深处（震源区附近）热应力值高达数十至百ＭＰａ，这可能偏大。但从浅层与中层的计算看，震源附近受到１０ＭＰａ左右的热应力控制是可能的。因此，本次地震可能与深部热力源有内在联系。n this paper the immediate preceding temperature variation field before the earthquake at Lancang-Gengma (October 1-28, 1988) was calculatedfrom the accurate measurements of the ground temperature-monitoring network of deep wells in Yunnan province. The correlation of this preceding thermal stress field with the earthquake was calculated and analyzed in detail, referring to Zhili Zhang's analytical method of thermal stress model〔1〕 and using the difference and the finite element methods for thermal stress.The results show:(1)There was intensive thermal abnormality before the earthquake, where the greatest gradient area of thermal abnormality was located near the location of the future intensive earthquake area, Lancang-Gengma. The period of greatest thermal abnormality appeared shortly before the earthquake (October 1-28, 1988). The greatest temperature variation of the thermal abnormality was 06℃ in the shallow layer (measured at the depth of about 200 meters), 13℃ in the middle layer (derived at the depth of 2 kilometers) and about 50℃ in the deep layer (derived at the depth of 8-13 kilometers near the focus of the earthquake).(2)The area of greatest thermal abnormality gradient, i.e., the greates thermal stress concentration area, co-localized with Lancang-Gengma, the area of the future intensive earthquake. The greatest thermal stress in this area was about 1 MPa in the shallow layer (at the depth of about 200 meters), 13-18 MPa in the middle layer (at the depth of about 2 kilometers), and 59-113 MPa in the deep layer (near the focus of the earthquake).(3)The thermal stress at the depth of 8-13 kilometers near the focus the earthquake was tens to hundreds of MPa, which might look too high. However, from the calculation in the shallow and middle layers, it was likely that the area near the focus of the earthquake was under the control of thermal stress of about 10 MPa. So the earthquake may have intrinsic correlation with deep thermal source.

关 键 词：地震前兆 热力场 震级 云南 澜沧-耿马地区 

分 类 号：P315.7[天文地球—地震学]