Abstract
The 1999 Hector Mine earthquake ruptured to the surface in eastern California, with >5 m peak right-lateral slip on the Lavic Lake fault. The cumulative offset and geologic slip rate of this fault are not well defined, which inhibits tectonic reconstructions and risk assessment of the Eastern California Shear Zone (ECSZ). With thermal infrared hyperspectral airborne imagery, field data, and auxiliary information from legacy geologic maps, we created lithologic maps of the area using supervised and unsupervised classifications of the remote sensing imagery. We optimized a data processing sequence for supervised classifications, resulting in lithologic maps over a test area with an overall accuracy of 71 ± 1% with respect to ground-truth geologic mapping. Using all of the data and maps, we identified offset bedrock features that yield piercing points along the main Lavic Lake fault and indicate a 1036 +27/−26 m net slip, with 1008 +14/−17 m horizontal and 241 +51/−47 m vertical components. For the contribution from distributed shear, modern off-fault deformation values from another study imply a larger horizontal slip component of 1276 +18/−22 m. Within the constraints, we estimate a geologic slip rate of <4 mm/yr, which does not increase the sum geologic Mojave ECSZ rate to current geodetic values. Our result supports previous suggestions that transient tectonic activity in this area may be responsible for the discrepancy between long-term geologic and present-day geodetic rates.
Highlights
The 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes resulted in two major surface ruptures in eastern California (Figure 1)
The Lavic Lake fault is located in the Bullion Mountains of the Mojave Desert, but there is limited information on the geology of this area, and the long-term cumulative offset along the fault is not well resolved
Estimates of long-term average geologic slip rates for the Eastern California Shear Zone (ECSZ) range from 8.3 ± 1.0 mm/yr since 12 Ma [21], to ≤6.2 ± 1.9 mm/yr since ~R7e5m0otke aSe[n2s2. 2].02T0h, 1e2d, xisFcOreRpPaEnEcRyRbEeVtIwEWeen geologic and geodetic slip rates in the ECSZ could be minim2 iozfe3d1 by incorporating the geologic slip rates of additional active faults
Summary
The 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes resulted in two major surface ruptures in eastern California (Figure 1). The Lavic Lake fault had not been formally named, its sense of displacement was unknown, and much of its surface trace was only mapped as an approximate location [14,15,16,17,18,19]. The Hector Mine Earthquake Geologic Working Group [13] formally named the fault after the Lavic Lake Playa (Figure 2a). A cumulative fault offset measurement was determined via geophysical methods: Jachens et al [20] estimated 3400 ± 800 m of right-lateral offset from displaced magnetic anomaly pairs within the Bullion Mountains. Estimates of long-term average geologic slip rates for the Eastern California Shear Zone (ECSZ) range from 8.3 ± 1.0 mm/yr since 12 Ma [21], to ≤6.2 ± 1.9 mm/yr since ~R7e5m0otke aSe[n2s2. 2].02T0h, 1e2d, xisFcOreRpPaEnEcRyRbEeVtIwEWeen geologic and geodetic slip rates in the ECSZ could be minim iozfe3d1 by incorporating the geologic slip rates of additional active faults
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
