The Pamir Frontal Thrust (PFT) of the Trans-Alai Range in Central Asia is the principal active fault of the intracontinental convergence zone between the Pamir and Tien Shan. Its northward propagation is reflected by frequent seismic activity and ongoing crustal shortening. Recent and historic earthquakes exhibit complex rupture patterns within and across seismotectonic segments bounding the Trans Alai, challenging our understanding of fault interaction and seismogenic potential. We provide paleoseismic data from five trenches along the central PFT segment (cPFT) and interpret five and possibly six paleoearthquakes that have ruptured since ∼7 ka and 16 ka, respectively. Our results indicate that at least three major earthquakes ruptured the full-segment length and possibly crossed segment boundaries with a recurrence interval of ∼1.9 kyr and potential magnitudes of up to M_w 7.4. We did not find evidence for great (i.e., M_w ≥8) earthquakes. However, discrepancies between slip and rupture extent during apparent partial segment ruptures in the western half of the cPFT, combined with significantly higher scarp offsets, indicate a more mature fault section with potential for future fault linkage. We estimate an average rate of horizontal motion for the cPFT of 4.1 ± 1.5 mm/yr during the past ∼5 kyr, which does not fully match the GNSS-derived present-day shortening rate of ∼10 mm/yr. This suggests a complex distribution of strain accumulation and potential slip partitioning between the cPFT and additional faults and folds within the Pamir that may be associated with a partially locked regional décollement.

中文翻译：

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帕米尔正面逆冲断层：全新世全段断裂及其对大陆碰撞区复杂段相互作用的影响

中亚跨阿莱山脉的帕米尔锋冲断层（PFT）是帕米尔高原与天山之间陆内辐合带的主要活动断层。频繁的地震活动和持续的地壳缩短反映了其向北传播。最近和历史上的地震在 Trans Alai 边界的地震构造段内和之间表现出复杂的破裂模式，挑战了我们对断层相互作用和发震潜力的理解。我们提供了沿中央 PFT 段 (cPFT) 的五个海沟的古地震数据，并分别解释了自 7 ka 和 16 ka 以来已经破裂的 5 次和可能的 6 次古地震。我们的结果表明，至少 3 次大地震破坏了全段长度，并可能以～1 的重复间隔跨越段边界。中号_W¯¯ 7.4。我们没有发现大地震（即M _w ≥ 8）的证据。然而，在 cPFT 西半部明显的部分段破裂期间滑动和破裂程度之间的差异，加上陡峭的偏移明显更高，表明更成熟的断层部分具有未来断层连接的潜力。我们估计过去 ~5 kyr 期间 cPFT 的平均水平运动率为 4.1 ± 1.5 mm/yr，这与 GNSS 得出的当今 ~10 mm/yr 的缩短率不完全匹配。这表明在 cPFT 和帕米尔内其他断层和褶皱之间的应变积累和潜在滑动划分的复杂分布，这可能与部分锁定的区域滑脱有关。