Elastic block and strain modeling of GPS data around the Haiyuan |
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Elastic block and strain modeling of GPS data around the Haiyuan
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Abstract Based on the dense GPS velocity field in the northeastern margin of the Tibetan Plateau from 1999 to 2016, we have produced the deformation and strain characteristics of the Haiyuan fault and the Liupanshan fault. Estimated long-term slip rate along the Haiyuan-Liupanshan fault zones show a gradual decrease from 6.4 ± 1.6 mm/yr at the Tuolaishan fault to 2.9 ± 1.2 mm/yr at the Southern Liupanshan fault. Left-lateral thrusting movement was inverted for the Xiangshan-Tianjingshan fault (XS-TJS), which has an average slip rate of 2.1 ± 3.4 mm/yr during the study period. We also calculated the heterogeneous distribution of interseismic coupling along the fault zones. Our result also shows the locking depth of the Tianzhu seismic gap is ∼22 km. The slip rate deficit, the seismic moment accumulation rate, and the Coulomb stress accumulation rate are high on the fault planes, whereas the second invariant of the strain rate is low at the surface. The Liupanshan fault is locked to a depth of ∼23 km, and the corresponding seismic moment accumulation rate on the fault plane is high, while the strain rate at the surface is low. The accumulated strain along the Tianzhu seismic gap and the Liupanshan fault could be balanced by earthquakes with magnitudes of Mw7.9 and Mw7.4, considering the absence of large earthquakes over the last 1000 years and 1400 years respectively. The Haiyuan segments had ruptured during 1920 Haiyuan earthquake, and the estimated locking depth for period 1999–2016 is 5–10 km. Its seismic moment accumulation rate at depth is low and the strain rate at the surface is high. Our result indicates that 70% of the strike-slip along the Haiyuan segments transforms into thrusting along the Liupanshan fault, while the remaining 30% is related to the orogeny of the Liupanshan. For slip between the Haiyuan fault and the XS-TJS, about 27–34% of the slip is partitioned on the XS-TJS.
中文翻译：
摘要 基于1999-2016年青藏高原东北缘密集的GPS速度场，我们得到了海原断裂和六盘山断裂的变形应变特征。估计沿海原-六盘山断裂带的长期滑动速率显示从托来山断裂的 6.4±1.6 mm/yr 逐渐下降到六盘山南部断裂的 2.9±1.2 mm/yr。象山-天景山断层（XS-TJS）的左旋逆冲运动在研究期间的平均滑动速率为2.1±3.4 mm / yr。我们还计算了沿断层带的地震间耦合的不均匀分布。我们的结果还表明，天柱地震间隙的锁定深度约为 22 公里。滑移率赤字，地震矩积累率，断面上的库仑应力积累率高，而应变率的第二不变量在地表低。六盘山断层锁定深度约23 km，断面上相应的地震矩积累率高，而地表应变率低。考虑到过去1000年和1400年没有发生大地震，天柱地震隙和六盘山断裂沿线的累积应变可以被Mw7.9和Mw7.4的地震平衡。海原段在 1920 年海原地震中破裂，1999-2016 年估计锁定深度为 5-10 公里。其深部地震矩累积率低，地表应变率高。结果表明，海原段70%的走滑转变为六盘山断裂逆冲，其余30%与六盘山造山运动有关。对于海原断层和 XS-TJS 之间的滑移，大约 27-34% 的滑移在 XS-TJS 上分区。 |
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