Using Daily Observations from Planet Labs Satellite Imagery to Separate the Surface Deformation Between the July 4th Mw 6.4 Foreshock and July 5th Mw 7.1 Mainshock During the 2019 Ridgecrest Earthquake Sequence.

On July 4th 2019 the Ridgecrest earthquake sequence began with a series of foreshocks including a Mw 6.4 event near Searles Valley, California. This was then followed 34 hours later by a Mw 7.1 mainshock located just 15 km to the north, with the earthquake sequence resulting in a complex array of intersecting faults. This earthquake sequence poses several interesting questions including, did the stress changes induced by the Mw 6.4 foreshock trigger the Mw 7.1 mainshock and what possible mechanism(s) could explain the occurrence of widespread secondary faulting surrounding both surface ruptures? However, most of the geodetic data (such as InSAR, lidar and optical satellite imagery), were acquired after both events had occurred making it difficult to discern which surface fractures happened when and their possible triggering mechanism. Here we provide a dataset composed of high-resolution optical imagery, pixel-value difference maps, .kmz fracturing mapping and horizontal deformation maps derived from subpixel image correlation, which can uniquely separate the surface fracturing and deformation between the foreshock and mainshock events that can help answer these questions. Separate imaging of the events is made possible by the daily acquisition of optical imagery by the Planet labs cubesat constellation, which acquired data between the two earthquakes, on the morning of July 4th and 5th, at 11.13 am and 17.12 pm PST, respectively, with the images acquired just 40 minutes after the foreshock and 56 minutes before the mainshock, respectively. Analysis from these optical imagery reveals the location of surface faulting that allow us to map their spatial extent and determine their timing. These data which we provide here can help guide and validate field survey observations to help understand which faults ruptured when, and constrain slip inversion models for more accurate estimates of stress changes induced by the foreshock imposed on the surrounding faults.