DEEP AND SHALLOW TECTONIC FEATURES AND EARTHQUAKES IN NORTH HENAN

By comprehensively analyzing the deep and shallow tectonic features of seismogeology and seismic activity in North Henan,the region is divided into the northern area and the southern area at the boundary,Bobi Xinxiang Shangqiu fault belt,and the two areas are separately discussed.In the northern area,the main tectonic line is NE direction,which is identical with the tectonic line in North China fault block region,the shallow tectonic presents fault uprise alternating with fault depression along the direction of regional tectonic line,and the Moho shows upwarping alternating with depression.In the southern area,the main tectonic line is basically NW direction,which is completely different from that in the northern area,the shallow tectonic in East Henan includes the secondary uprise and depression on the basis of whole subsidence,and deep structures show the large scale Moho upwarping where there are secondary depressions.West Henan block shows the whole uprise,the main type of tectonics are faults,which control the formation and evolution of a series of down faulted basins,and the Moho is depressed.Acording to historical and modern earthquakes and combined with the shallow tectonic and deep structure,it is thought that there are risks for occurrence of moderate and strong earthquakes in Tangyin graben and Sanmenxia Lingbao basin.