Why is any of this useful?
Reassessing multi-fault rupture in diffuse fault zones in the ECSZ
Accounting for complex, multi-fault rupture in the Panamint Valley transtensional relay includes deformation previously not accounted for in regional slip budgets. Additionally, our new tectonogeomorphic mapping, geochronologic dating and kinematic analysis presents evidence for up to four kinematically related ruptures between the Ash Hill and PVTR faults, and up to four spatio-temporally related earthquakes between the Panamint and Ash Hill-PVTR fault systems during the last ~4 - 5 ka. The Eastern California Shear Zone has displayed historical examples of multi-fault ruptures across km-scale fault zones with combinations of dextral, normal, and sinistral motion on kinematically related fault systems. Strain partitioning on two (or more) different faults equates to larger rupture and greater magnitude earthquakes (if in a single event), and greater stress release and strain accommodation by a single area. While historic examples of multi-fault rupture exist, paleoseismic examples of multi-fault rupture in the ECSZ are rare. Modern seismicity supports that complex multi-fault rupture is a common rupture style in young fault networks such as the ECSZ. Therefore, zones where diffuse faulting occurs between adjacent fault strands must be identified to re-characterize previously interpreted rupture barriers as strain transfer zones capable of assisting in earthquake “jumping”. Complex, multi-fault ruptures, such as those observed in the PVTR appear to be links between larger fault zones where stress and strain may be transferred across greater distances. Analyzing the spatial and temporal heterogeneity of fault rerupturing in areas with complex surface ruptures cannot be accurately resolved by isolating paleoseismic rupture on a single fault strand. For instance, ruptures in young alluvium may not always occur on a previously ruptured strand (Figure 8). Young, immature ruptures appear to commonly occur on new strands, supporting the prevalence of historic rupture on previously unmapped (or new) surface traces. The 2019 Ridgecrest earthquake and 2010 El Mayor Cucapah earthquake involved surface ruptures on previously unmapped faults, and the historical examples of multi-fault ruptures (1992 Landers and 1999 Hector Mine earthquakes) linked previously discontinuous faults. The PVTR demonstrates how high-resolution tectonogeomorphic mapping in zones of complex rupture is necessary to quantifying rupture magnitude and kinematics in immature fault zones. In this study, we generate a high-resolution surface fan chronology and high-resolution digital surface models to resolve smaller scarps and offsets in areas of diffuse, distributed deformation in young Holocene alluvium. These methods are incredibly effective at resolving paleoseismicity in areas of high structural complexity in young fault zones where paleoseismicity cannot be resolved with current lidar, trenching and numerical dating datasets alone. We propose that using these methods, currently unmapped, complex, diffuse ruptures may be identified in the ECSZ that may provide evidence for structural or seismogenic links between major fault zones capable of producing large, damaging earthquakes.