MICRO-EARTHQUAKES IN THE SHIZIGOU OILFIELD, QINGHAI, AND THEIR GEOLOGICAL SIGNIFICANCE
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摘要: 通过对柴达木盆地西部狮子沟地区一年多的微地震监测数据的分析处理, 发现该区微地震活动比较频繁, 总体走向北西, 且多集中在该区盆山过渡带北西走向的花土沟断裂北东侧2km深度附近。通过对地震与钻孔分布之间的关系和地震发生频次对数与震级线性关系的斜率b值的分析, 本文认为, 虽然油井注水等因素对研究区内微地震事件具有一定的诱发作用, 但大部分地震事件仍主要与断裂及其次级构造有关。Abstract: A large number of high-quality seismic data are recorded in the Shizigou oilfield of the western Qaidam basin by monitoring micro-earthquakes for more than one year.After processing and analyzing these data, the authors find that micro-earthquakes occur relatively frequently in the study area and are mainly concentrated at ~2 km depth on the NE side of the NW-trending Huatugou fault in the basinmountain transition zone of the area.Analyses of the relation between earthquakes and oil well distribution and the slope b in the linear relation between log frequency and magnitude show that microearthquakes in the study area are mainly related to the Huatugou fault and its secondary structures though fluid injection through the wells has a certain microearthquake-inducing effect in the area.
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Key words:
- micro-earthquake /
- fault activity /
- Shizigou oilfield /
- western Qaidam basin
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图 2 狮子沟8个台站(IG01-IG08)记录到同一微地震的地震波及其震相提取示意图
Figure 2. Seismograms for one micro-earthquake recorded by 8 seismic stations (IG01-IG08) at Shizigou and illustration of seismic phase picking.
图 3 研究区内微地震分布
灰色影像表示高程(单位:m)。圆圈表示震中; 三角表示地震台站; 标注为符号的表示钻孔。图中黑色虚线标识盆山交界, 为花土沟断裂在地表出露的大概位置, 标出的倾向为本文推测。黑实线为一条穿过研究区的垂直剖面的位置, 该剖面上的地震分布显示在图 2中。
Figure 3. Epicenter distribution for micro-earthquakes in the study region
图 4 地震频次与震级关系图
图中直线是对大于-0.25级地震进行的地震频次的对数与震级M关系的线性拟合
Figure 4. Relation between occurrence frequency and magnitude of micro-earthquakes
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