欧亚大陆东缘存在一个巨型深断裂系统——基于卫星重力的新发现

通过对卫星重力数据的精细处理,发现欧亚大陆东缘存在一个规则分布的重力异常组合,这个异常组合与中国大陆上的已知断裂严格对应。SinoProbe探测计划实施的反射地震探测出这些断裂下方存在Moho破裂,幔源物质上涌,剩余重力异常,莫霍面破裂,高密度的幔源物质上涌和深断裂之间存在密切联系。依照这个联系规律,对已有断裂的延伸补充,显示出欧亚大陆东缘存在一个巨型深断裂系统,主断裂带南起中国广州向北延伸直至鄂霍次克海,绵延逾3000 km。沿主断裂带东侧近似等间距的平行分布着9条北东向断裂,北东向断裂向东入海至大陆边缘。采用数值方法模拟了断裂系统的形成过程,在菲律宾板块和太平洋板块近NW方向构造力的作用下,欧亚大陆东缘产生NNE向走滑断层,其东侧生成彼此平行,间距大体相等的派生断层。断层形成过程中,Moho破裂,大量地幔物质上涌,形成中国东部中生代以来的巨量火山岩浆活动,控制了内生金属矿床的分布。这个断裂系统近代还在活动,导致了郯城8.5级大地震和长白山的火山喷发。

A Huge Deep Fault System at the East Edge of Eurasia: The New Tectonic Interpretation Based on Satellite Gravity

Through the subtle processing of satellite gravity data, a regular distribution of gravity anomaly combination was found at the east edge of Eurasia. In order to study geological significance of the combination of these anomalies, the authors adopted gravity inversion based seismic constraints, and the result shows that there exist positive relationships between the discovered gravity anomaly, the uplift of the Moho and the deep fault. According to the gravity anomalies and geological information, the authors found a huge deep fault system at the east edge of Eurasia. The main fault stretches more than 3000 km from Guangzhou northward to the sea of Okhotsk. On the eastern side of the main fault zone, there are 9 parallel faults distributed approximately equidistantly; these faults trend NE and extend to the continental margin into the sea. The authors used numerical simulation method to verify the formation of this fault system: under the horizontal action of force, SN-trending strike slip faults were generated in the east of Eurasian Continent, and then a series of transform fault deep into the lithosphere came into being. In the formation process of the fault system, a large quantity of mantle matter surged upward, resulted in the uplift of Moho, and then triggered massive volcanic- magmatic activities after Mesozoic in eastern China and controlled the distribution of endogenic metallic deposits. The fault system remains active at present, which led to the magnitude 8.5 earthquake in Tancheng and volcanic eruption in the Changbai Mountains.