青藏高原东北缘岩石圈有效弹性厚度与地震分布关系  

Relationship between the lithosphere effective elastic thickness and earthquake distribution in the northeastern margin of the Tibetan Plateau

作　　者：苏子旺 鲁宝亮[1,2,3] 李柏森 朱武 SU ZiWang;LU BaoLiang;LI BoSen;ZHU Wu(School of Geological Engineering and Geomatics,Chang'an University,Xi'an 710054,China;National Engineering Research Center of Offshore Oil and Gas Exploration,Beijing 100028,China;Key Laboratory of Western Mineral Resources and Geological Engineering,Ministry of Education,Chang'an University,Xi'an 710054,China)

机构地区：[1]长安大学地质工程与测绘学院,西安710054 [2]海洋油气勘探国家工程研究中心,北京100028 [3]西部矿产资源与地质工程教育部重点实验室,西安710054

出　　处：《地球物理学报》2024年第2期520-533,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42374168,41904106);中央高校基本科研业务费(300102260202,300102262902)联合资助.

摘　　要：岩石圈有效弹性厚度(T_(e))表征岩石圈综合力学强度,对理解区域深部构造孕震环境具有重要意义.青藏高原东北缘地质构造复杂,强烈地震活动频发.为进一步了解该区域深部岩石圈力学性质特征及其与地震活动的关系,本文利用基于Fan小波的谱方法,使用WGM2012重力异常数据、ETOPO1地形数据和CRUST1.0模型,通过导纳和相关联合反演计算了青藏高原东北缘的岩石圈有效弹性厚度(T_(e))与荷载比(F).结果显示研究区T_(e)整体呈明显的东高西低分布,青藏块体T_(e)变化剧烈,西部高值(>40 km)和东部低值(<20 km)共存;鄂尔多斯地块T_(e)较高(>30 km),变化相对平缓;荷载比F存在局部西南高,巴颜喀拉和羌塘地块荷载比F较高(>0.5),说明以地下荷载为主,其他地块荷载比F较低(<0.2),以地表荷载为主.鄂尔多斯地块结构稳定,岩石圈强度较大,T_(e)值较高;内部构造活动性微弱,深部物质密度横向变化较小,岩石圈所受荷载以地表为主,荷载比F较低.柴达木地块东部与巴颜喀拉地块东部可能发生有下地壳流,岩石圈较为软弱,T_(e)值较低;巴颜喀拉地块内部与鲜水河断裂的荷载比F较高,岩石圈所受荷载以地下为主,可能是地壳物质向东流动导致岩石圈深部物质密度横向变化较大引起的.通过对比分析研究区T_(e)和T_(e)梯度、F和F梯度与地震之间的对应关系,发现地震一般发生在区域相对低T_(e)值、T_(e)梯度值和荷载比F梯度值较大的区域,震级较小的地震多发生在荷载比F较小的地区,6级以上强震则较多发生在荷载比F约为0.1和0.8的区域.因此,岩石圈有效弹性厚度T_(e)值较低、T_(e)梯度和荷载比F梯度较大的地区,更易出现地震.The lithosphere effective elastic thickness(T_(e)represents the comprehensive mechanical strength of the lithosphere,which is of great significance for understanding the seismogenic environment of regional deep structure.The geological structure of the northeast margin of the Tibetan Plateau is complex and strong earthquake activity occurs frequently.We aim to further understand the mechanical properties of the deep lithosphere in the region and its relationship with seismic activity.This article uses the Fan wavelet spectral method to calculate the effective elastic thickness(T_(e)and load ratio(F)of the lithosphere on the northeastern edge of the Tibetan Plateau through joint inversion of admittance and correlation.WGM2012 gravity anomaly,ETOPO1 topography,and CRUST1.0 model are used.The results show that Te in the whole study area is obviously high in the east and low in the west.Te in the Qinghai-Tibet block changes dramatically.The high value(>40 km)in the west and the low value(<20 km)in the east coexist.Te in the Ordos block is relatively high(>30 km)and changes smoothly.The load ratio F is locally high in the southwest.The load ratio F of the Bayan Har and the Qiangtang blocks are relatively high(>0.5),indicating that the underground load is the main load.While other blocks are relatively low(<0.2),indicating that the surface load is the main load.The Ordos block has stable structure,strong lithosphere and high Te value;the internal tectonic activity is weak,the lateral change of deep material density is small,the load on the lithosphere is mainly from surface,so the load ratio F is small.The east of Qaidam block and the east of Bayan Har block may have lower crustal flow,with weak lithosphere and low Te values.The load ratio F in the interior of the Bayan Har block and the Xianshuihe fault is high,and the load on the lithosphere is mainly from underground,which may be caused by the large lateral changes in the deep lithosphere because of the eastward flow of crustal materials.By comparing and analyzing t

关 键 词：有效弹性厚度 荷载比 重力异常 地震分布 

分 类 号：P315[天文地球—地震学]