This report details the luminescence ages and characteristics of four (4) samples that were collected by Jessica Jobe and Rich Briggs of the USGS. These samples are from Holocene and Pleistocene sediments offset by a fault that is exposed in a road cut. The roadcut is in Puerto Rico at 18.003828 and -67.140249 with an elevation of 13.5 m. The sample depths from the modern surface varied from 0.6 m (top) for GB-OSL-4 to 1.6 m for GB-OSL-2 (deepest sample).

As part of the Coastal Sediment Availability and Flux and Defense Advanced Research Protection Agency (DARPA) Reefense projects, scientists from the U.S. Geological Survey (USGS) and St. Petersburg Coastal and Marine Science Center (SPCMSC) conducted a nearshore geophysical survey to map and characterize the stratigraphy of back-barrier bays near Panama City, Florida (FL) in June 2022. This data release serves as an archive of sediment vibracores collected from St. Andrew Bay, April 23–27, 2023. Sediment vibracore and lithology data provide assessments on the composition and age of sediments below the seafloor. This information can provide information about sub-seafloor structure that can inform the siting and assess the stability of artificial and natural oyster reef structures that will be placed on the seafloor during the Reefense project’s later phases.

As part of the Coastal Sediment Availability and Flux and Defense Advanced Research Protection Agency (DARPA) Reefense projects, scientists from the U.S. Geological Survey (USGS) and St. Petersburg Coastal and Marine Science Center (SPCMSC) conducted a nearshore geophysical survey to map and characterize the stratigraphy of back-barrier bays near Panama City, Florida (FL) in June 2022. This data release serves as an archive of sediment vibracores collected from St. Andrew Bay, April 23–27, 2023. Sediment vibracore and lithology data provide assessments on the composition and age of sediments below the seafloor. This information can provide information about sub-seafloor structure that can inform the siting and assess the stability of artificial and natural oyster reef structures that will be placed on the seafloor during the Reefense project’s later phases.

The data release includes 35 new luminescence ages and 3 new radiocarbon ages. The new age data further brackets the ages of the Las Vegas basin Quaternary stratigraphy and provide new constraints on the timing of Quaternary fault activity.

This report summarizes the dating results from sedimentary deposits sampled by the Coastal and Marine Science Center and analyzed at the USGS Luminescence Geochronology Laboratory. Within this report, we detail the luminescence measurement, equivalent dose determination, and dating-related calculations. We recommend that this report be included as the supplementary material for any publication (s) that use the ages within this report.

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.

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.

The following report summarizes the dating results from Aeolian deposits within and around Edwards Air Force Base in California. Within this report, we detail the methodology used by the USGS Luminescence Geochronology Laboratory to obtain ages including sample preparation methods, luminescence measurement, equivalent dose determination, and dating related calculations. We recommend that this report be included as the supplementary material for any publication(s) that use the ages within this report. This version supersedes all previous age estimates and reports.

The following report summarizes the dating results from Aeolian deposits within and around Edwards Air Force Base in California. Within this report, we detail the methodology used by the USGS Luminescence Geochronology Laboratory to obtain ages including sample preparation methods, luminescence measurement, equivalent dose determination, and dating related calculations. We recommend that this report be included as the supplementary material for any publication(s) that use the ages within this report. This version supersedes all previous age estimates and reports.

This data release documents neotectonic mapping of fault-related features on high-resolution lidar-derived topography, data documenting an exposure of the South Lajas fault, and summary information for active and potentially active Quaternary faults on the island of Puerto Rico. The data documenting the exposure of the South Lajas fault include detailed unit descriptions, radiocarbon sample descriptions, data, and results, and a structure-from-motion-derived orthophoto mosaic of the exposure. Luminescence data and ages for the exposure can be found in a related data release. These datasets are associated with the manuscript: Thompson Jobe, J. A. R. Briggs, K. S. Hughes, J. Joyce, R. Gold, S. Mahan, H. Gray, L. Strickland (in review). Neotectonic mapping of Puerto Rico.