Stepovers in strike-slip fault systems play important roles in controlling the propagation of earthquake ruptures, depending partially on the competition between the stepover width and the coseismic slip gradient approaching the step. The 1920 Mw 7.9 Haiyuan earthquake is the most recent major earthquake that has occurred along the Haiyuan fault. The earthquake rupture broke through multiple stepovers along the fault and finally ended at the 4 km-wide Jingtai pull-apart basin (releasing stepover) at the western end. To understand the process of this termination of the Haiyuan earthquake rupture, we conducted detailed mapping of the surface rupture geometry, coseismic slip measurement and slip gradient calculation in the vicinity of the endpoint based on the 0.2 m-resolution SfM-derived DEM along the 20 km section east of the Jingtai pull-apart basin. Combining coseismic slip measurements from this study and published slip data from fieldwork in the 1980s, we calculated slip gradients of 84–160 cm/km as the rupture approached the Jingtai releasing stepover. These values are high for the 4 km-wide Jingtai releasing stepover compared to those from a dataset of worldwide historical earthquakes compiled by Elliott et al. (2009). The high values imply that the rupture could have a relatively high likelihood of breaching through the Jingtai releasing stepover. Alternatively, the slip gradient may be overestimated. Detailed mapping and field investigation, however, show that the rupture may extend ~1.86 km farther west of the end location indicated in previous studies. We acquired the new slip gradient with lower value of 50–82 cm/km, which is still considerably high compared to dataset of Elliott et al. (2009). We speculate that the slip gradient could be larger variation along the stepover boundary to stop fault slip in different geologic setting. Another factor control slip termination is related to fault properties. Creep along the southern boundary fault of the Jingtai stepover, a velocity-strengthening region, may also have played a role in stopping the rupture at this location. Our observations further indicate that the increasing LOS velocity of InSAR data within the Jingtai stepover is probably related to fault behavior rather than a nontectonic signal of subsidence.

走滑断层系统中的跨距在控制地震破裂的传播方面起着重要作用，部分取决于跨距宽度和接近该阶跃的同震滑动梯度之间的竞争。1920兆瓦7.9 海原地震是海原断裂带发生的最近一次大地震。地震破裂沿断层多次跨越，最终在西端4km宽的景泰拉分盆地（释放跨越）结束。为了解海原地震破裂终止的过程，我们基于 0.2 m 分辨率的 SfM 衍生 DEM 沿 20景泰拉分盆地以东公里断面。结合这项研究的同震滑动测量和 1980 年代野外工作公布的滑动数据，我们计算出当破裂接近景泰释放步距时 84-160 厘米/公里的滑动梯度。与 Elliott 等人编制的全球历史地震数据集相比，4 公里宽的景泰释放步距的这些值很高。(2009)。高值意味着破裂可能有相对较高的可能通过景泰释放步距破裂。或者，滑移梯度可能被高估。然而，详细的测绘和实地调查表明，破裂可能会在先前研究中指出的终点位置向西延伸约 1.86 公里。我们获得了较低值 50-82 cm/km 的新滑移梯度，与 Elliott 等人的数据集相比，这仍然相当高。(2009)。我们推测滑移梯度可能沿着跨步边界有​​更大的变化，以阻止不同地质环境下的断层滑移。另一个控制滑动终止的因素与故障特性有关。沿景泰台阶南边界断层的蠕变，一个速度加强区，也可能在阻止该位置的破裂中发挥了作用。我们的观察进一步表明，景泰阶跃内 InSAR 数据的 LOS 速度增加可能与断层行为有关，而不是与沉降的非构造信号有关。