Precise Relative Earthquake Magnitudes from Cross Correlation

Cleveland, K. Michael; Ammon, Charles J.

doi:10.1785/0120140329

Cited by 27 publications

(26 citation statements)

References 10 publications

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“…Using relative magnitude calculations documented in Cleveland and Ammon [] and listed in Table S1, we estimate that the relative moments of the 1994 and 2008 events differ by about 10%, which is consistent with Boettcher and McGuire []. If we assume that the 2008 event is a repeat of the 1994 and there was no slip between events and each event released all the plate motion strain accumulated between the events, based on MORVEL [ DeMets et al ., ], the approximate seismic slip is ~64 cm (using ~49 mm/yr).…”

Section: Relative Relocation Results For the Northeast Pacificmentioning

confidence: 99%

Precise relative locations for earthquakes in the northeast Pacific region

2015

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Double‐difference methods applied to cross‐correlation measured Rayleigh wave time shifts are an effective tool to improve epicentroid locations and relative origin time shifts in remote regions. We apply these methods to seismicity offshore of southwestern Canada and the U.S. Pacific Northwest, occurring along the boundaries of the Pacific and Juan de Fuca (including the Explorer Plate and Gorda Block) Plates. The Blanco, Mendocino, Revere‐Dellwood, Nootka, and Sovanco fracture zones host the majority of this seismicity, largely consisting of strike‐slip earthquakes. The Explorer, Juan de Fuca, and Gorda spreading ridges join these fracture zones and host normal faulting earthquakes. Our results show that at least the moderate‐magnitude activity clusters along fault strike, supporting suggestions of large variations in seismic coupling along oceanic transform faults. Our improved relative locations corroborate earlier interpretations of the internal deformation in the Explorer and Gorda Plates. North of the Explorer Plate, improved locations support models that propose northern extension of the Revere‐Dellwood fault. Relocations also support interpretations that favor multiple parallel active faults along the Blanco Transform Fault Zone. Seismicity of the western half of the Blanco appears more scattered and less collinear than the eastern half, possibly related to fault maturity. We use azimuthal variations in the Rayleigh wave cross‐correlation amplitude to detect and model rupture directivity for a moderate size earthquake along the eastern Blanco Fault. The observations constrain the seismogenic zone geometry and suggest a relatively narrow seismogenic zone width of 2 to 4 km.

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Section: Relative Relocation Results For the Northeast Pacificmentioning

confidence: 99%

Precise relative locations for earthquakes in the northeast Pacific region

2015

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“…Although future work could reestimate all event magnitudes as M w [e.g., Cleveland and Ammon , ], at this stage we elect to extend, rather than replace, the network magnitudes. Thus, cognizant of the trade‐offs, we adopt the pragmatic approach of empirically matching catalog magnitude scaling and extending this scaling to newly detected events.…”

Section: Methodsmentioning

confidence: 99%

Fluid‐faulting evolution in high definition: Connecting fault structure and frequency‐magnitude variations during the 2014 Long Valley Caldera, California, earthquake swarm

2016

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An extended earthquake swarm occurred beneath southeastern Long Valley Caldera between May and November 2014, culminating in three magnitude 3.5 earthquakes and 1145 cataloged events on 26 September alone. The swarm produced the most prolific seismicity in the caldera since a major unrest episode in 1997–1998. To gain insight into the physics controlling swarm evolution, we used large‐scale cross correlation between waveforms of cataloged earthquakes and continuous data, producing precise locations for 8494 events, more than 2.5 times the routine catalog. We also estimated magnitudes for 18,634 events (~5.5 times the routine catalog), using a principal component fit to measure waveform amplitudes relative to cataloged events. This expanded and relocated catalog reveals multiple episodes of pronounced hypocenter expansion and migration on a collection of neighboring faults. Given the rapid migration and alignment of hypocenters on narrow faults, we infer that activity was initiated and sustained by an evolving fluid pressure transient with a low‐viscosity fluid, likely composed primarily of water and CO2 exsolved from underlying magma. Although both updip and downdip migration were observed within the swarm, downdip activity ceased shortly after activation, while updip activity persisted for weeks at moderate levels. Strongly migrating, single‐fault episodes within the larger swarm exhibited a higher proportion of larger earthquakes (lower Gutenberg‐Richter b value), which may have been facilitated by fluid pressure confined in two dimensions within the fault zone. In contrast, the later swarm activity occurred on an increasingly diffuse collection of smaller faults, with a much higher b value.

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“…Our method differs from Rubinstein and Ellsworth (2010) who used singular value decomposition to measure relative amplitudes. To convert the relative amplitude measurements for all possible pairs and stations in a RES to absolute magnitudes we perform an inversion of the differential magnitudes similar to that in Cleveland and Ammon (2015). The inversion across stations helps suppress outliers due to unknown gain changes at a particular station.…”

Section: Relative Magnitudesmentioning

confidence: 99%

A Comprehensive Search for Repeating Earthquakes in Northern California: Implications for Fault Creep, Slip Rates, Slip Partitioning, and Transient Stress

Waldhauser

Schaff

2021

JGR Solid Earth

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Repeating earthquakes−earthquakes that rupture the same fault area with sources of similar magnitude and mechanism−are playing an increasingly important role in the study of fault processes and behavior, and have the potential to improve hazard assessment, earthquake forecast, and seismic monitoring capabilities. The recurrence interval of large repeating earthquakes is a crucial parameter when estimating hazard probabilities (Ellsworth, 1995; WGCEP, 1999). Repeating earthquakes, in particular smaller magnitude events, often produce sequences of remarkable periodicity that indicate characteristic behavior (Ellsworth, 1995;Nadeau & Johnson, 1998;Vidale et al., 1994). Because recurrence models that describe cycles of repeating earthquakes have at least modest predictive power (Matthews et al., 2002;Zechar & Nadeau, 2012) they play an increasingly important role in determining earthquake risk.

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Precise Relative Earthquake Magnitudes from Cross Correlation

Cited by 27 publications

References 10 publications

Precise relative locations for earthquakes in the northeast Pacific region

Precise relative locations for earthquakes in the northeast Pacific region

Fluid‐faulting evolution in high definition: Connecting fault structure and frequency‐magnitude variations during the 2014 Long Valley Caldera, California, earthquake swarm

A Comprehensive Search for Repeating Earthquakes in Northern California: Implications for Fault Creep, Slip Rates, Slip Partitioning, and Transient Stress

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