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Abstract. Fault slip is a complex natural phenomenon involving multiple spatiotemporal scales from seconds to days to weeks. To understand the physical and chemical processes responsible for the full fault slip spectrum, a multidisciplinary approach is highly recommended. The Near Fault Observatories (NFOs) aim at providing high-precision and spatiotemporally dense multidisciplinary near-fault data, enabling the generation of new original observations and innovative scientific products. The Alto Tiberina Near Fault Observatory is a permanent monitoring infrastructure established around the Alto Tiberina fault (ATF), a 60 km long low-angle normal fault (mean dip 20°), located along a sector of the Northern Apennines (central Italy) undergoing an extension at a rate of about 3 mm yr−1. The presence of repeating earthquakes on the ATF and a steep gradient in crustal velocities measured across the ATF by GNSS stations suggest large and deep (5–12 km) portions of the ATF undergoing aseismic creep. Both laboratory and theoretical studies indicate that any given patch of a fault can creep, nucleate slow earthquakes, and host large earthquakes, as also documented in nature for certain ruptures (e.g., Iquique in 2014, Tōhoku in 2011, and Parkfield in 2004). Nonetheless, how a fault patch switches from one mode of slip to another, as well as the interaction between creep, slow slip, and regular earthquakes, is still poorly documented by near-field observation. With the strainmeter array along the Alto Tiberina fault system (STAR) project, we build a series of six geophysical observatory sites consisting of 80–160 m deep vertical boreholes instrumented with strainmeters and seismometers as well as meteorological and GNSS antennas and additional seismometers at the surface. By covering the portions of the ATF that exhibits repeated earthquakes at shallow depth (above 4 km) with these new observatory sites, we aim to collect unique open-access data to answer fundamental questions about the relationship between creep, slow slip, dynamic earthquake rupture, and tectonic faulting.
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Survey and Continuous GNSS in the Vicinity of the July 2019 Ridgecrest Earthquakes
Abstract The Mw 6.4 and Mw 7.1 Ridgecrest, California, earthquakes of July 2019 occurred within 34 hr of each other on conjugate strike-slip faults in the Mojave Desert, just north of the central Garlock fault. Here, we present the results of a survey of 18 Global Navigation Satellite Systems (GNSS) sites conducted in the immediate aftermath of the earthquakes, including five sites that recorded the motion of the second earthquake after having been set up immediately following the first, as well as processed results from continuous GNSS sites throughout the region. Our field work in response to the earthquakes provides additional constraints on the ground displacement due to both earthquakes, complementing data from a spatially sparser network of continuously recording GNSS sites in the area, as well as temporally sparser Interferometric Synthetic Aperture Radar data that were able to capture a combined deformation signal from the two earthquakes.
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- PAR ID:
- 10142495
- Date Published:
- Journal Name:
- Seismological Research Letters
- ISSN:
- 0895-0695
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1785/0220190324
