The Thickness of Seismogenic Layer Under the Areas Surrounding the Ordos Block, Northern China
The Thickness of Seismogenic Layer Under the Areas Surrounding the Ordos Block, Northern China
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DOI：
10.1007/s00024-002-8750-7
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发表时间：
2002-09
影响因子：
2
通讯作者：
C. Qin
中科院分区：
文献类型：
--
作者：
C. Qin
- 用地震方法计算了中国北部鄂尔多斯地块下的孕震层厚度分布。之所以选择这个区块，是因为它的稳定性、其边界周围复杂的构造以及数据集的完整性。20世纪该地区曾发生过几次强震，其中最大的一次发生在鄂尔多斯西南部的海原，1920年海原M=8.4。鄂尔多斯周围的大断层大多是走滑断层。根据古登堡-里希特关系，计算了从小震到大震的自相似性的断裂点(即震级饱和Mc)。在偏移量与断层长度成正比的L模型(Scholz，1982,1990,1994)的假设下，孕震层的厚度(WC)与Tomc直接相关。为了更好地显示孕震层厚度的变化，并保证结果的可靠性，采用了150个事件的移动单元，移动步长为0.1度。为了利用现有数据集，使用了“均值法”，即根据最新的完整数据信息，使现有数据集成为“完整的”数据集，从而使数据涵盖整个时间段。结果表明，鄂尔多斯西南部、西北和东部的平均孕震层厚度分别约为30、9和17 km。厚度一般从西南向东北递减。这种空间变化与大量微震的最大深度分布相吻合，相关系数约为0.88，与莫霍面深度相吻合。
— A seismic approach was used to calculate the thickness distribution of the seismogenic layer under the block Ordos in northern China. This block was chosen because of its stability, the complicated tectonics around its boundaries and the completeness of the data set. Several strong earthquakes occurred in this area in the 20thcentury, with the largest one (Haiyuan,M= 8.4, 1920) in the southwest of the Ordos. Most of the large faults around the Ordos are strike-slip ones. The breaking point (i.e., the saturation of earthquake magnitudesMc) of the self-similarity from small to large events based on the Gutenberg-Richter relation is calculated. Under the assumption of theLmodel which expresses that the offset is proportional to the length of the fault (Scholz, 1982, 1990, 1994), the thickness (Wc) of the seismogenic layer is directly related toMc. To display smoothly the change of the thickness of the seismogenic layer and to ensure the reliability of the results, a moving cell of 150 events, with a moving step of 0.1 degree, was adopted. To take advantage of the existing data set, the “mean value method,” which is based on the latest complete data information to make the existing data set a `complete' one, was used to extrapolate it so that the data covers the whole time period. The results show that the average thickness of the seismogenic layer in the southwest, in the northwest and in the east of the Ordos is around 30, 9 and 17 km, respectively. The thickness generally decreases from the southwest to the northeast. This kind of spatial variation is in agreement with the maximum depth distribution of large amounts of microearthquakes, with the correlation coefficient to be about 0.88, and the Moho depth.