Foreshocks and Their Potential Deviation from General Seismicity

Seif, Stefanie; Zechar, J. D.; Mignan, Arnaud; Nandan, Shyam; Wiemer, Stefan

doi:10.1785/0120170188

Cited by 36 publications

(49 citation statements)

References 41 publications

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“…Our results strengthen previous reports that earthquake activity precursory to mainshocks can sometimes deviate from simple clustering properties (as modeled by ETAS; Lippiello et al., 2019; Seif et al., 2019). Our approach is however different.…”

Section: Discussionsupporting

confidence: 92%

“…For example, compared to Seif et al. (2019), we seek to explain the last 20 days prior to mainshocks knowing all past seismicity (including activity in the last 20 days), by comparing what number of earthquakes would be “normally” expected (in the sense of ETAS) to the observed number. In contrast, Seif et al.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, Seif et al. (2019) compared observations to the number of foreshocks predicted by ETAS simulations not constrained by past seismicity. Our method is indeed close to the residual analyses of Ogata (1988), (1989), (1992), and (2003), which is here performed individually on a set of 53 mainshocks thanks to the improved completeness of the QTM dataset.…”

Section: Discussionmentioning

confidence: 99%

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Rare Occurrences of Non‐cascading Foreshock Activity in Southern California

Moutote

Marsan

Lengliné

et al. 2021

Geophysical Research Letters

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Earthquakes preceding large events are commonly referred to as foreshocks. They are often considered as precursory phenomena reflecting the nucleation process of the main rupture. Such foreshock sequences may also be explained by cascades of triggered events. Recent advances in earthquake detection motivates a reevaluation of seismicity variations prior to mainshocks. Based on a highly complete earthquake catalog, previous studies suggested that mainshocks in Southern California are often preceded by anomalously elevated seismicity. In this study, we test the same catalog against the Epidemic Type Aftershock Sequence model that accounts for temporal clustering due to earthquake interactions. We find that 10/53 mainshocks are preceded by a significantly elevated seismic activity compared with our model. This shows that anomalous foreshock activity is relatively uncommon when tested against a model of earthquake interactions. Accounting for the recurrence of anomalies over time, only 3/10 mainshocks present a mainshock‐specific anomaly with a high predictive power.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Rare Occurrences of Non‐cascading Foreshock Activity in Southern California

Moutote

Marsan

Lengliné

et al. 2021

Geophysical Research Letters

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“…Earthquake clustering is manifested most clearly by aftershock sequences consisting of numerous smaller events (aftershocks) following a larger earthquake (mainshock) in its space‐time proximity (e.g., Kisslinger, ; Omori, ; Shcherbakov et al, ; Utsu & Ogata, ). Foreshocks are a related form of clustering involving premainshock events associated with smaller number and smaller areas than those for aftershocks (e.g., Ellsworth, ; Jones, ; Mignan, ; Ogata et al, ; Seif et al, ). Foreshocks‐mainshock‐aftershock sequences are assumed to be related causally through triggering by dynamic, static, and longer‐term postseismic stress‐transfer mechanisms (e.g., Ben‐Zion et al, ; Hill et al, ; King & Cocco, ).…”

Section: Introductionmentioning

confidence: 99%

Earthquake Declustering Using the Nearest‐Neighbor Approach in Space‐Time‐Magnitude Domain

Zaliapin

Ben‐Zion

2020

JGR Solid Earth

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We introduce an algorithm for declustering earthquake catalogs based on the nearest-neighbor analysis of seismicity. The algorithm discriminates between background and clustered events by random thinning that removes events according to a space-varying threshold. The threshold is estimated using randomized-reshuffled catalogs that are stationary, have independent space and time components, and preserve the space distribution of the original catalog. Analysis of catalog produced by the Epidemic Type Aftershock Sequence model demonstrates that the algorithm correctly classifies over 80% of background and clustered events, correctly reconstructs the stationary and space-dependent background intensity, and shows high stability with respect to random realizations (over 75% of events have the same estimated type in over 90% of random realizations). The declustering algorithm is applied to the global Northern California Earthquake Data Center catalog with magnitudes m ≥ 4 during 2000-2015; a Southern California catalog with m ≥ 2.5, 3.5 during 1981-2017; an area around the 1992 Landers rupture zone with m ≥ 0.0 during 1981-2015; and the Parkfield segment of San Andreas fault with m ≥ 1.0 during 1984-2014. The null hypotheses of stationarity and space-time independence are not rejected by several tests applied to the estimated background events of the global and Southern California catalogs with magnitude ranges Δm < 4. However, both hypotheses are rejected for catalogs with larger range of magnitudes Δm > 4. The deviations from the nulls are mainly due to local temporal fluctuations of seismicity and activity switching among subregions; they can be traced back to the original catalogs and represent genuine features of background seismicity.We analyze global seismicity, earthquakes in California, and a synthetic catalog produced by the ETAS model. Table 1 summarizes information about the examined data.

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“…Focusing on moderate up to intermediate (Mw<5) mainshock magnitudes, after the original paper by Brodsky 6 , several studies [7][8][9][10][11][12] have shown that the number of foreshocks in instrumental catalogs is larger than the one expected according to normal earthquake clustering models. This result is also in agreement with a recent study 13 , before Mw4 mainshocks, which uses a highresolution earthquake catalog.…”

mentioning

confidence: 99%

Recognizing the waveform of a foreshock

Lippiello¹,

Petrillo²,

Godano³

2020

Preprint

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The 2011 Mw9.1 Tohoku, Japan, earthquake is the paradigmatic example of an earthquake anticipated by a significant foreshock activity, with a Mw7.3 earthquake occurred two days before, within about 10 km 1. Recent results 2 show that statistically relevant changes can be found in the magnitude distribution after the Mw7.3 foreshock but the discrimination between normal and foreshock activity still remains a scientific challenge 3. Here we show that the envelope of the ground velocity recorded after the Mw7.3 foreshock presents an atypical sawtooth profile very different from the one observed after other earthquakes 4. We interpret this profile as the consequence of the locked state of the mainshock fault which reduces the possibility of the foreshock to trigger its own aftershocks. We find a similar sawtooth profile after other Mw6+ foreshocks followed within 10 days by a larger earthquake, as in the case of the 2014 Mw8.1 Iquique, Chile, sequence. This observation allows us to define a level of concern, simply extracted from the first 45 minutes of the recording waveform, associated to the occurrence of a larger earthquake. A test of the method for 47 Mw6+ worldwide earthquakes gives precise warning in time and space after all the 10 earthquakes followed by a larger one with only 2 false alerts.

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Foreshocks and Their Potential Deviation from General Seismicity

Cited by 36 publications

References 41 publications

Rare Occurrences of Non‐cascading Foreshock Activity in Southern California

Rare Occurrences of Non‐cascading Foreshock Activity in Southern California

Earthquake Declustering Using the Nearest‐Neighbor Approach in Space‐Time‐Magnitude Domain

Recognizing the waveform of a foreshock

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