摘要：Along-strike variation in scarp morphologyreflects differences in a fault's geomorphic and structural development andcan thus indicate fault rupture history and mechanical segmentation.Parameters that define scarp morphology (height, width, slope) are typicallymeasured or calculated manually. The time-consuming manual approach reducesthe density and objectivity of measurements and can lead to oversight ofsmall-scale morphological variations that occur at a resolution impracticalto capture. Furthermore, inconsistencies in the manual approach may also leadto unknown discrepancies and uncertainties between, and also within,individual fault scarp studies. Here, we aim to improve the efficiency,transparency and uniformity of calculating scarp morphological parameters bydeveloping a semi-automated Scarp PARameTer Algorithm (SPARTA). We compareour findings against a traditional, manual analysis and assess theperformance of the algorithm using a range of digital elevation model (DEM)resolutions. We then apply our new algorithm to a 12m resolution TanDEM-XDEM for four southern Malawi fault scarps, located at the southern end of theEast African Rift system: the Bilila–Mtakataka fault (BMF) and three previouslyunreported scarps – Thyolo, Muona and Malombe. All but Muona exhibitfirst-order structural segmentation at their surface. By using a 5mresolution DEM derived from high-resolution(50cmpixel−1) Pleiades stereo-satellite imagery for theBilila–Mtakataka fault scarp, we quantify secondary structural segmentation.Our scarp height calculations from all four fault scarps suggest that if eachscarp was formed by a single, complete rupture, the slip–length ratio foreach earthquake exceeds the maximum typical value observed in historicalnormal faulting earthquakes around the world. The high slip–length ratiostherefore imply that the Malawi fault scarps likely formed in multipleearthquakes. The scarp height distribution implies the structural segments ofboth the BMF and Thyolo fault have merged via rupture of discrete faults(hard links) through several earthquake cycles, and the segments of theMalombe fault have connected via distributed deformation zones (soft links).For all faults studied here, the length of earthquake ruptures may thereforeexceed the length of each segment. Thus, our findings shed new light on theseismic hazard in southern Malawi, indicating evidence for a number of large(Mw 7–8) prehistoric earthquakes, as well as providing a newsemi-automated methodology (SPARTA) for calculating scarp morphologicalparameters, which can be used on other fault scarps to infer structuraldevelopment.
