摘要
同震位移量作为地震地表破裂带的要素之一,其大小不仅反映了地震的震级,而且也影响到对地震断层滑动速率和大震重现间隔长短的估计。1556年华县8级地震造成了83万多人的死亡和失踪,是鄂尔多斯周缘断陷活动带活跃期造成地震灾害伤亡最严重的1次地震,但长期以来缺少该次地震地表破裂带准确的同震位移量。文中通过对华山山前断裂李家坡剖面和渭南塬前断裂蔡郭村等剖面地貌学、钻探及探槽等古地震研究手段,首次较准确地获得了1556年华县大地震时华山山前断裂带华县李家坡6m同震垂直位移、渭南塬前断裂带赤水蔡郭村7m及瓜底村6m的同震垂直位移。这是由断层两盘同一地层位错量测得到的同震垂直位移量,与以往仅通过地表断层陡坎量测估算的同震位移有一定的差别。
Coseismic displacement plays a role in earthquake surface rupture,which not only reflects the magnitude scale but also has effect on estimates of fault slip rate and earthquake recurrence intervals.A great historical earthquake occurred in Huaxian County on the 23 rdJanuary 1556,however,there was lack of surface rupture records and precise coseismic vertical displacements. It＇s known that the1556 Huaxian earthquake was caused by Huashan front fault and Weinan plateau front fault,which are large normal faults in the east part of the southern boundary faults in Weihe Basin controlling the development of the basin in Quaternary. Here,we made a study on three drilling sites in order to unveil the coseismic vertical displacements.It is for the first time to get the accurate coseismic vertical displacements,which is 6m at Lijiapo site of Huashan front fault,7m at Caiguocun site,and 6m at Guadicun site of Weinan plateau front fault. These coseismic displacements measured based on same layers of drilling profiles both at footwall and hanging wall are different from the results measured by former geomorphological fault scarps. It＇s estimated that some scarps are related with the nature reformation and the human beings＇ activities,for example,fluviation or terracing field,instead of earthquake acticity,which leads to some misjudgment on earthquake displacements. Moreover, the vertical displacements from the measurement of geomorphological scarps alone do not always agree with the virtual ones. Hence,we assume that the inconsistency between the results from drilling profiles and geomorphological scarps in this case demonstrates that the fault scarp surface may have been demolished and rebuilt by erosion or human activities.
出处
《地震地质》
EI
CSCD
北大核心
2016年第1期22-30,共9页
Seismology and Geology
基金
国家自然科学基金青年科学基金(41502205)资助
关键词
1556年华县地震
同震垂直位移
华山山前断裂
渭南塬前断裂
1556 Huaxian earthquake
coseismic vertical displacement
Huashan front fault
Weinan plateau front fault
