活动地块多层次构造单元划分及强震活动的相互关联——以鄂尔多斯活动地块和华北平原活动地块为例

Regionalization of Multi-ordering Tectonic Units in Active Massif in Relation to Strong Earthquake Activities——Taking Ordos Active Massif and North-China Plain Active Massif as Examples

一、前言张文佑先生在我国较早地提出了断块构造概念,指出:“综合分析地质和地球物理,特别是地层和岩石、航磁、重力等资料以及结合模拟试验,得知中国大地构造不仅现在,而且在过去都具有以断裂运动为特征的块断构造性质。”,并指出大陆地质构造的断块概念概括了各种不同等级大地构造的“块断属性”。在第四纪活动构造的研究中。

Regionalization of multi-ordering tectonic units in the Ordos active massif and strong earthquake tectonic features in the North China Plain active massif have been discussed in this paper, and the similarity and difference in strong earthquake seismo-genic tectonic features of the two massif compared. Within the Ordos active massif, 5 tectonic units of second order can be delineated, 4 of them are active, and the other one is stable. The 4 active tectonic units are of down-faulted basin belts; and most of them can further be classified into 2～5 units of the third order bounded and controlled by 1～3 major active faults. These major active faults are the dominated place for strong earthquake activities in the Ordos massif. However, Quaternary strata cover North China Plain massif. It is hard to further delineate it into tectonic sub-units precisely as lack of enough data, though some active tectonic evidence shows they seem exist. In recent several hundred of years, there have had 9 earthquakes with M≥7 occurred in North China Plain massif. Three of them occurred in Bohai gulf, and other 3 occurred on one side of NNE-trending depressions; but their seismo-genic tectonics were NWW-trending faults, implying their neogenic. The rest of 3 occurred along NNE-trending faults in North China Plain massif. There have had 4 historical large earthquakes with M≥8 in the 4 second-order tectonic units in Ordos active massif. While several historical shocks with M=7～8 have had occurred in North China Plain massif and its surrounding areas. Active tectonic studies show that the recurrence interval of large earthquakes for a single fault zone are about 2,000～4,000a. While the recurrence interval of large earthquakes for one tectonic unit of second or third-order is 1～2 times shorter in numerical order than that for a single fault zone.