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Abstract We develop an earthquake simulator to study the partitioning of seismic/aseismic slip and dynamics of Earthquakes on a Heterogeneous strike‐slip Fault (HFQsim) using a generalized model of a discrete fault governed by static/dynamic friction and creep in an elastic half‐space. Previous versions of the simulator were shown to produce various realistic seismicity patterns (e.g., frequency‐magnitude event statistics, hypocenter and slip distributions, temporal occurrence) using friction levels and creep properties that vary in space but are fixed in time. The new simulator incorporates frictional heat generation by earthquake slip leading to temperature rises, subsequent diffusion cooling into the half space, and time‐dependent creep on the fault. The model assumes a power law dependence of creep velocity on the local shear stress, with temperature‐dependent coefficients based on the Arrhenius equation. Temperature rises due to seismic slip produce increased aseismic slip, which can lead to further stress concentrations, aftershocks, and heat generation in a feedback loop. The partitioning of seismic/aseismic slip and space‐time evolution of seismicity are strongly affected by the temperature changes on the fault. The results are also affected significantly by the difference between the static and kinetic friction levels. The model produces realistic spatio‐temporal distribution of seismicity, transient aseismic slip patterns, mainshock‐aftershock sequences, and a bimodal distribution of earthquakes with background and clustered events similar to observations. The HFQsim may be used to clarify relations between fault properties and different features of seismicity and aseismic slip, and to improve the understanding of failure patterns preceding large earthquakes.
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Microseismicity at the Time of a Large Creep Event on the Calaveras Fault is Unresponsive to Stress Changes
The potential relationship between surface creep and deeper geological processes is unclear, even on one of the world’s best-studied faults. From June to August 2021, a large creep event with surface slip of more than 16 mm was recorded on the Calaveras fault in California, part of the San Andreas fault system. This event initially appeared to be accompanied by along-fault migration of seismicity, suggesting it penetrated to depth. Other studies have suggested that surface creep events are likely a shallow feature, unrelated to deep seismicity. To provide more detail on the relationship between earthquakes, surface creep, and potential aseismic slip at seismogenic depth, we tripled the number of earthquakes in the Northern California Earthquake Catalog in the region of the creep event for all of 2021. This was accomplished by implementing earthquake detection techniques based on both template matching (EQCorrscan) and AI-based automatic earthquake phase picking (PhaseNet). After manual inspection, the detected earthquakes were first located using Hypoinverse and subsequently relocated via GrowClust. Our enhanced catalog indicates that the spatiotemporal pattern of earthquakes here is not strongly influenced by the creep event and is better explained by structural heterogeneity than transient stress changes, indicating a decoupling of seismicity rate and surficial creep on this major fault.
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- Award ID(s):
- 2031457
- PAR ID:
- 10638697
- Publisher / Repository:
- Seismica
- Date Published:
- Journal Name:
- Seismica
- Volume:
- 3
- Issue:
- 2
- ISSN:
- 2816-9387
- 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/10.26443/seismica.v3i2.1337
