Detection of small earthquakes with dense array data: example from the San Jacinto fault zone, southern California

Meng, Haoran; Ben‐Zion, Yehuda

doi:10.1093/gji/ggx404

Cited by 34 publications

(36 citation statements)

References 23 publications

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“…(a) A histogram of all detected air traffic events from Julian day 129 to 157, 2014, with about 31 air traffic events per day and relatively quiet time during the local night. (b) A histogram of high quality small candidate earthquakes detected Julian day 146 by Meng and Ben‐Zion (). (c) Hourly mean absolute amplitude of stacked waveforms of the entire dense array in Julian day 146, 2014.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of Airplanes and Helicopters Recorded by a Dense Seismic Array Near Anza California

Meng

Ben‐Zion

2018

JGR Solid Earth

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We observe frequent air traffic events in continuous seismic waveforms recorded for about 30 days by 1,108 vertical geophones in a tight array on the San Jacinto fault zone. The waveforms of the air traffic events resemble tremor or collections of small earthquakes. However, time‐frequency analysis reveals clear Doppler effects that can be modeled with basic equations and fitted well with parameters corresponding to airplanes and helicopters. The flying traces can be inverted by fitting the parameters at each station across the entire array. About 31 air traffic events are detected per day in the relatively remote study area, with peak activity from about 8:00 to 18:00 and significantly fewer events between 23:00 and 4:00 local time. The average event duration is about 200 s, so they cover together >7% of the day. To estimate the total time covered by earthquakes, we derive a scaling relation logτ(M) = 0.41M + 0.89 between earthquake duration and magnitudes using data of 266 earthquakes in the magnitude range 0 ≤ M ≤ 3. The results indicate that in most places, the duration of air traffic events is likely to exceed considerably the total time covered by earthquakes.

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Section: Discussionmentioning

confidence: 99%

Characteristics of Airplanes and Helicopters Recorded by a Dense Seismic Array Near Anza California

Meng

Ben‐Zion

2018

JGR Solid Earth

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“…Qin et al 2018), detect seismic events (e.g. Inbal et al 2016;Li et al 2018;Meng & Ben-Zion 2018) and track anthropogenic footprints (e.g. Riahi & Gerstoft 2015).…”

Section: Discussion Smentioning

confidence: 99%

Investigating microearthquake finite source attributes with IRIS Community Wavefield Demonstration Experiment in Oklahoma

Fan

McGuire

2018

Geophysical Journal International

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An earthquake rupture process can be kinematically described by rupture velocity, duration and spatial extent. These key kinematic source parameters provide important constraints on earthquake physics and rupture dynamics. In particular, core questions in earthquake science can be addressed once these properties of small earthquakes are well resolved. However, these parameters of small earthquakes are poorly understood, often limited by available data sets and methodologies. The Incorporated Research Institutions for Seismology Community Wavefield Experiment in Oklahoma deployed ∼350 three-component nodal stations within 40 km 2 for a month, offering an unprecedented opportunity to test new methodologies for resolving small earthquake finite source properties in high resolution. In this study, we demonstrate the power of the nodal data set to resolve the variations in the seismic wavefield over the focal sphere due to the finite source attributes of an M2 earthquake within the array. The dense coverage allows us to tightly constrain rupture area using the second moment method even for such a small earthquake. The M2 earthquake was a strike-slip event and unilaterally propagated towards the surface at 90 per cent local S-wave speed (2.93 km s −1). The earthquake lasted ∼0.019 s and ruptured L c ∼70 m and W c ∼45 m. With the resolved rupture area, the stress-drop of the earthquake is estimated as 7.3 MPa for M w 2.3. We demonstrate that the maximum and minimum bounds on rupture area are within a factor of two, much lower than typical stressdrop uncertainty, despite a suboptimal station distribution. The rupture properties suggest that there is little difference between the M2 Oklahoma earthquake and typical large earthquakes. The new three-component nodal systems have great potential for improving the resolution of studies of earthquake source properties.

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“…Spatially dense arrays can be used for detection and analysis of sources that have a signal‐to‐noise ratio (SNR) close to and below 1, allowing for the identification of earthquakes, tremors, or other signals that are buried in the noise (e.g., Ben‐Zion et al, ; Ross et al, ; Schmandt & Clayton, ; Shelly et al, ). Advances in techniques for detecting small earthquakes and tremor (Aguiar & Beroza, ; Barrett & Beroza, ; Hammer et al, ; Meng & Ben‐Zion, ; Perol et al, ; Reynen & Audet, ; Ross et al, ; Yoon et al, ) increase the need to properly decipher nontectonic transient signals in the waveforms that are originating at the surface from anthropogenic and other natural phenomenon (e.g., Inbal et al, ; Meng & Ben‐Zion, ; Riahi & Gerstoft, ). Extracting the correct information from seismic waveforms requires a clear understanding of local and regional anthropogenic sources, and the coupling of atmospheric processes with the solid Earth to properly identify differences between tectonic and nontectonic signals.…”

Section: Introductionmentioning

confidence: 99%

“…The Sage Brush Flat (SGB) site on the San Jacinto Fault Zone (SJFZ) southeast of Anza, California is the location of a previous dense geophone deployment (Ben‐Zion et al, ) and various studies associated with detailed imaging of the subsurface material (Hillers et al, ; Mordret et al, ; Roux et al, ) and detection of small earthquakes and air‐traffic events (Meng & Ben‐Zion, , ). Using a frequency‐domain matched‐field processing technique involving beamforming and backprojection of continuous array data (Corciulo et al, ; Kuperman & Turek, ), very small events were detected at the SGB site and were found to cluster near structures, fences, and within the vegetation.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Ground Motion Generated by Wind Interaction With Trees, Structures, and Other Surface Obstacles

et al. 2019

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Analysis of continuous seismic waveforms from a temporary deployment at Sage Brush Flats on the San Jacinto fault reveals earthquake‐ and tremor‐like signals generated by the interaction of wind with obstacles above the surface. Tremor‐like waveforms are present at the site during wind velocities above 2 m/s, which occur for 70% of the deployment duration. The response to the wind has significant spatial variability with highest ground motions near large surface objects. The wind‐related signals show ground velocities that exceed the average ground motions of M1.0–1.5 earthquakes for 6–31% of the day. Waveform spectra indicate a modulation of amplitude that correlates with wind velocity and distance from local structures. Earthquake‐like signals are found to originate from local structures and vegetation, and are modified on length scales of tens of meters. Transient signals originating beyond the study area are also observed with amplitudes greater than some microseismic events. The wind‐related ground motions contribute to local high‐frequency seismic noise. Some of these signals may be associated with small failures of the subsurface material. During elevated wind conditions a borehole seismometer at a depth of 148 m shows increased energy in the 1–8‐Hz band that is commonly used for earthquake and tremor detection. The wind‐related earthquake‐ and tremor‐like signals should be accounted for in earthquake detection algorithms due to the similar features in both time and frequency domains. Proper recognition of wind‐related ground motions can contribute to understanding the composition of continuous seismic waveforms and characterize mechanical properties of the shallow crust.

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Detection of small earthquakes with dense array data: example from the San Jacinto fault zone, southern California

Cited by 34 publications

References 23 publications

Characteristics of Airplanes and Helicopters Recorded by a Dense Seismic Array Near Anza California

Characteristics of Airplanes and Helicopters Recorded by a Dense Seismic Array Near Anza California

Investigating microearthquake finite source attributes with IRIS Community Wavefield Demonstration Experiment in Oklahoma

Characteristics of Ground Motion Generated by Wind Interaction With Trees, Structures, and Other Surface Obstacles

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