Rupture process for micro-earthquakes inferred from borehole seismic recordings

Taira, T.; Dreger, Douglas S.; Nadeau, R. M.

doi:10.1007/s00531-015-1217-8

Cited by 11 publications

(11 citation statements)

References 44 publications

(39 reference statements)

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“…Our inversion is restricted to a single 1 km × 1 km fault plane that is divided into 961 32 × 32 m subfaults. We tested a smoothing factor of 200, following Taira et al [2015] in estimating the rupture processes of M~3 Hayward-Fault earthquakes. With a grid search approach, we then explored an optimal combination of the rupture velocity and risetime to maximize the goodness-of-fit of the MRF, defined as the variance reduction.…”

Section: Resultsmentioning

confidence: 99%

Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

Shelly

Taira

Prejean

et al. 2015

Geophysical Research Letters

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Faulting and fluid transport in the subsurface are highly coupled processes, which may manifest seismically as earthquake swarms. A swarm in February 2014 beneath densely monitored Mammoth Mountain, California, provides an opportunity to witness these interactions in high resolution. Toward this goal, we employ massive waveform‐correlation‐based event detection and relative relocation, which quadruples the swarm catalog to more than 6000 earthquakes and produces high‐precision locations even for very small events. The swarm's main seismic zone forms a distributed fracture mesh, with individual faults activated in short earthquake bursts. The largest event of the sequence, M 3.1, apparently acted as a fault valve and was followed by a distinct wave of earthquakes propagating ~1 km westward from the updip edge of rupture, 1–2 h later. Late in the swarm, multiple small, shallower subsidiary faults activated with pronounced hypocenter migration, suggesting that a broader fluid pressure pulse propagated through the subsurface.

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Section: Resultsmentioning

confidence: 99%

Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

Shelly

Taira

Prejean

et al. 2015

Geophysical Research Letters

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“…[]. At the same time, this observation indicates that it is not sufficient to only consider the average stress drop to examine the healing process and also that the actual slip distribution is needed to reveal spatial and temporal variations of a stress drop within the area of rupture [e.g., Taira et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Changes in repeating earthquake slip behavior following the 2004 Parkfield main shock from waveform empirical Green's functions finite‐source inversion

et al. 2016

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Finite‐source inversions are performed using small earthquake waveforms as empirical Green's functions (eGf) to investigate the rupture process of repeating earthquakes along the San Andreas Fault in Parkfield, California. The eGf waveform inversion method is applied to a repeating Mw 2.1 Parkfield earthquake sequence using three‐component velocity waveforms recorded by an array of borehole seismometers. The obtained models show a circular slip distribution with a ~20 m radius, a 3.0–4.2 cm average slip of the main asperity, and peak displacement of 10.6–13.5 cm. The static stress drop distribution shows that the main asperity has a peak stress drop of 69.5–94.7 MPa. The inversion results support an earlier finding by Dreger et al. (2007) that high‐strength asperities exist in the rupture areas of the Mw 2.1 events at Parkfield. In addition, notable temporal peak slip and stress drop reduction was observed after the 2004 Parkfield event while the average value remains constant (~12 MPa) over time. These events may represent mechanically strong sections of the fault, surrounded by regions that are undergoing continuous deformation (creep), Given repeated loading of the strong asperities, it would be expected that these similar repeating earthquakes should also have very similar slip distributions since surrounding regions are deforming aseismically. There are small differences in the waveforms of these repeating earthquakes, and this could be because of rupture nucleation points not being in exactly the same location within the region of the fault that is capable of stick‐slip behavior. Our result indicates that waveform slip inversion is needed to reveal spatial and temporal variations of the stress drop within the rupture area to improve understanding of fault healing and rupture mechanics.

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“…Older studies usually dealt with rupture properties of single earthquakes (Jost et al, 1998;Li et al, 1995), and only recently, larger sets of events were examined for complexities or directivity (Abercrombie et al, 2017;Calderoni et al, 2015;Kane et al, 2013;Lengliné & Got, 2011;Ross & Ben-Zion, 2016). Recent studies also analyzed microseismic events (Dreger et al, 2007;Folesky et al, 2015Folesky et al, , 2016Taira et al, 2015) in an effort to connect with the scales from physical rupture modeling in the laboratory and numerical modeling (e.g., Kaneko & Shearer, 2014Lapusta et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Patterns of Rupture Directivity of Subduction Zone Earthquakes in Northern Chile

2018

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We perform a systematic directivity analysis of local seismic events west off the coast of northern Chile. An empirical Green's function technique is applied to a selection of events from a time period from 2008 to 2016 in the vicinity of the rupture area of the MW8.1 Iquique megathrust earthquake in 2014. We compute rupture directivity for 293 events of magnitudes between ML 2.6 and ML 5.3. We find a strong preference of rupture orientations subparallel to the convergence vector of the Nazca plate relative to the South‐American plate. The preferred rupture direction is downdip. We speculate that the reason for the dominating rupture direction could be a lateral limitation of available rupture directions by the repeating earthquake‐like nature of the observed events combined with a material contrast at the subduction interface which, according to the bimaterial effect, favors the downdip rupture direction.

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Rupture process for micro-earthquakes inferred from borehole seismic recordings

Cited by 11 publications

References 44 publications

Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

Changes in repeating earthquake slip behavior following the 2004 Parkfield main shock from waveform empirical Green's functions finite‐source inversion

Patterns of Rupture Directivity of Subduction Zone Earthquakes in Northern Chile

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