Data Release for Luminescence: Surficial Mapping of the Central Panamint Valley, Inyo County, California
Several historic, multi-fault ruptures in the Eastern California Shear Zone (ECSZ) reinforce the need to understand how this rupture style contributes to seismic hazard in complex and diffuse fault zones. Several historic earthquakes in the ECSZ, the 1992 Landers, the 1999 Hector Mine, and the 2019 Ridgecrest rupture sequence, involved complex and multi-fault rupture. However, paleoseismic evidence of multi-fault ruptures in the ECSZ is poorly resolved in the rock record. Here I investigate paleoseismic evidence for complex rupture in Panamint Valley, located ~50 km northeast of the 2019 Ridgecrest ruptures. Late Holocene scarps in the 10 km-wide transtensional relay between the Ash Hill and Panamint Valley faults display surface rupture geometries analogous to those produced during the 1992 Landers and 1999 Hector Mine earthquakes. I produce a 1:4000 scale tectonogeomorphic map of the 40 km² area between the Ash Hill and Panamint Valley faults using my locally-calibrated relative-age alluvial fan chronology and using NCALM lidar DEMs and aerial imagery to identify ruptures. I bracket earthquakes with post-IR feldspar infrared-stimulated luminescence dating of offset deposits. I record vertical and lateral offsets at over 250+ locations using field mapping and backslipped reconstructions of newly generated high resolution (5 cm) drone-based structure from motion digital surface models. My mapping shows that the transtensional relay consists of 100+ fault strands that occur in parallel and en échelon arrays 5-7 km in length, with spacings of 1s to 100s of meters. Using my relative-age fan stratigraphy, geochronologic dating of offset deposits, and relative cumulative offset, I identify four late Holocene ruptures at ~0.3 – ~0.7 ka, ~0.7 – 2.4 ka, ~2.6 – 3.6 ka, and ~3.6 – 4.2 ka. Displacement magnitude per event ranges from 0.6 – 1.0 m of lateral slip and 0 – 0.2 m of dip slip. Displacement-length scaling relationships suggest that these mapped faults cannot rupture independently of a larger fault system. My results show overlap in the timing of ruptures in the transtensional relay, on the Ash Hill and Panamint faults, and that the Ash Hill and transtensional relay are kinematically similar. These similarities suggest this region acts as a zone for complex strain transfer between the Ash Hill and Panamint faults over multiple earthquake cycles. These relationships may support a geometric link at depth or the reoccupation of preexisting weaknesses at depth capable of transferring strain over larger distances.
|Data Release for Luminescence: Surficial Mapping of the Central Panamint Valley, Inyo County, California
|Shannon A Mahan, Emma T Krolczyk, Aubrey LaPlante, Christine Regalla
|USGS Digital Object Identifier Catalog
|Geosciences and Environmental Change Science Center