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AbstractAnalysis of patterns of faulting and hydrogeology, stratigraphic and sedimentologic studies, and luminescence dating of aeolian deposits in China Lake basin provide new perspectives on the origins and development of Late Holocene dunes and sand ramps in the seismically active Indian Wells Valley of eastern California. Aeolian dune and sand sheet deposits were sourced from alluvial material derived from granitic rocks of the south-eastern Sierra Nevada and are concentrated in areas with sand-stabilizing phreatophyte vegetation influenced by high groundwater levels along the active oblique-normal Little Lake and Paxton Ranch faults, which locally form barriers to groundwater flow. Three episodes of sand accumulation are recognized (2.1 ± 0.1 to 2.0 ± 0.1 ka, 1.8 ± 0.2 to 1.6 ± 0.2 ka, and 1.2 ± 0.1 to 0.9 ± 0.1 ka) during conditions in which sediment supplied to the basin during periods of enhanced rainfall and runoff was subsequently reworked by wind into dunes and sand ramps at the transition to more arid periods. Understanding the role tectonics plays in influencing the hydrogeology of seismically active lake basins provides insights to accurately interpret landscape evolution and any inferences made on past hydroclimate variability in a region.

ABSTRACT The 2019 Ridgecrest earthquake sequence produced a 4 July M 6.5 foreshock and a 5 July M 7.1 mainshock, along with 23 events with magnitudes greater than 4.5 in the 24 hr period following the mainshock. The epicenters of the two principal events were located in the Indian Wells Valley, northwest of Searles Valley near the towns of Ridgecrest, Trona, and Argus. We describe observed liquefaction manifestations including sand boils, fissures, and lateral spreading features, as well as proximate non-ground failure zones that resulted from the sequence. Expanding upon results initially presented in a report of the Geotechnical Extreme Events Reconnaissance Association, we synthesize results of field mapping, aerial imagery, and inferences of ground deformations from Synthetic Aperture Radar-based damage proxy maps (DPMs). We document incidents of liquefaction, settlement, and lateral spreading in the Naval Air Weapons Station China Lake US military base and compare locations of these observations to pre- and postevent mapping of liquefaction hazards. We describe liquefaction and ground-failure features in Trona and Argus, which produced lateral deformations and impacts on several single-story masonry and wood frame buildings. Detailed maps showing zones with and without ground failure are provided for these towns, along with mapped ground deformations along transects. Finally, we describe incidents of massive liquefaction with related ground failures and proximate areas of similar geologic origin without ground failure in the Searles Lakebed. Observations in this region are consistent with surface change predicted by the DPM. In the same region, geospatial liquefaction hazard maps are effective at identifying broad percentages of land with liquefaction-related damage. We anticipate that data presented in this article will be useful for future liquefaction susceptibility, triggering, and consequence studies being undertaken as part of the Next Generation Liquefaction project.

Surface rupture from the 2019 Ridgecrest earthquake sequence, initially associated with the M-w 6.4 foreshock, occurred on 4 July on a-17 km long, northeast-south-west-oriented, left-lateral zone of faulting. Following the M-w 7.1 mainshock on 5 July (local time), extensive northwest-southeast-oriented, right-lateral faulting was then also mapped along a similar to 50 km long zone of faults, including subparallel splays in several areas. The largest slip was observed in the epicentral area and crossing the dry lakebed of China Lake to the southeast. Surface fault rupture mapping by a large team, reported elsewhere, was used to guide the airborne data acquisition reported here. Rapid rupture mapping allowed for accurate and efficient flight line planning for the high-resolution light detection and ranging (lidar) and aerial photography. Flight line planning trade-offs were considered to allocate the medium (25 pulses per square meter [ppsm]) and high-resolution (80 ppsm) lidar data collection polygons. The National Center for Airborne Laser Mapping acquired the airborne imagery with a Titan multispectral lidar system and Digital Modular Aerial Camera (DiMAC) aerial digital camera, and U.S. Geological Survey acquired Global Positioning System ground control data. This effort required extensive coordination with the Navy as much of the airborne data acquisition occurred within their restricted airspace at the China Lake ranges.

Many modern weapon systems depend on Global Positioning System (GPS) to achieve midcourse or terminal accuracy requirements. This reliance on GPS navigation dictates that weapon system test facilities be equipped to create realistic GPS jamming (GPSJ) environments. The Naval Air Warfare Center Weapons Division (NAWCWPNS) at China Lake is developing a system of free-space jammers to create a realis- tic GPS threat environment. The goal of this effort is to yield a high-degree of commonality among outdoor jamming systems and the ones used in NAWCWPNS' Navigation Laboratory and anechoic facilities. The ability to successfully conduct free-space GPS jamming tests in the continental US is highly problematic due to exten- sive civilian use of GPS. This paper begins by discussing the major issue related to conducting free-space GPS jamming tests: interference with commercial and other DoD GPS users. Following this discussion, the paper focuses on proposed mitigation methods modeled after NAWCWPNS' energetic materials testing process. The paper concludes with an analy- sis of a scenario based on an example free-space GPS jammer.

he designed and implemented instrumentation for energetic materials testing and atmospheric physics research. Matt has been a member of the GPS/INS Systems Section since 1989, and has been involved with design and implementation of missile hardware-in-the-loop simulations, navigation error analysis and GPS jamming efforts. He is currently tasked in the development and analysis of GPS jammer systems. Kenea Maraffio received her BS in Electrical Engineering from Arizona State University. Employed by NAWCWPNS, China Lake, in 1991, she worked on development of phased-array antenna control software and radome compensation algorithms. In 1993 Kenea developed software for real-time remote control of the Stanford Telecom 7200 GPS satellite simulator. Kenea is currently developing software for remotely controlling a smart, free-space GPS jammer. ABSTRACT Many modern weapon systems depend on Global Positioning System (GPS) to achieve midcourse or terminal accuracy requirements. This reliance on GPS navigation dictates that weapon system test facilities be equipped to create realistic GPS jamming (GPSJ) environments. The Naval Air Warfare Center Weapons Division (NAWCWPNS) at China Lake is developing a system of free-space jammers to create a realistic GPS threat environment. The goal of this effort is to yield a high-degree of commonality among outdoor jamming systems and the ones used in NAWCWPNS' Navigation Laboratory and anechoic facilities. The ability to successfully conduct free-space GPS jamming tests in the continental US is highly problematic due to extensive civilian use of GPS. This paper begins by discussing the major issue related to conducting free-space GPS jamming tests: interference with commercial and other DoD GPS users. Following this discussion, the paper focuses on proposed mitigation methods modeled after NAWCWPNS' energetic materials testing process. The paper concludes with an analysis of a scenario based on an example free-space GPS jammer.