Earthquake recurrence models fail when earthquakes fail to reset the stress field

Tormann, Thessa; Wiemer, Stefan; Hardebeck, Jeanne L.

doi:10.1029/2012gl052913

Cited by 28 publications

(30 citation statements)

References 23 publications

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“…In our view, there is overwhelming evidence that the b value variations are not caused by random artifacts. Our publications on Parkfield, starting with Wiemer and Wyss [] and including formal testing [ Schorlemmer et al ., ] have revealed a near identical spatial pattern of b based on several independent data sets, tested prospectively, and consistently observed for independent time periods [e.g., Tormann et al ., ]. They are also consistent with independent geophysical data, such as geodetic observations that image the asperity/barrier distribution.…”

Section: Artifacts Caused By Under Sampling?supporting

confidence: 86%

Reply to Comment by Kamer on “Systematic survey of highresolution b value imaging along Californian faults: Inference on asperities”

Tormann

Wiemer

2014

JGR Solid Earth

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Kamer [2014] questions the suitability of the distance exponential weighted (DEW) sampling to map b values (introduced by Tormann et al. [2014]), and in particular the approach of the synthetic experiment to select suitable imaging parameters. We do not agree with the criticism, which is neither original nor correct, as detailed below. But we initially like to point out that it is largely not pertinent to our publication in the first place, because the objective of the Tormann et al.[2014] study was not to derive an automated and self-optimizing way to map b values as Kamer [2014] implies. Our goal was targeted toward imaging potential asperities, low b value structures along faults, of sizes capable of accommodating M6+ events, i.e., structures of~20-40 km length. Based on physical reasoning, we introduced a novel distance weighting to sample local seismicity data, and since this has not been published before, we compared, as one should, how the different new and old sampling approaches perform in resolving a realistic synthetic target structure. We chose the final sampling parameter (distance decay λ) based on the performance in this synthetic experiment.Kamer [2014] addresses three main aspects to underline his impression that our approach would not be applicable to seismicity analysis: (1) the well-known and often published sample size and absolute valuedependent uncertainty of b values; (2) the obvious and previously published finding that large sampling radii (he suggests R max = 40 km and negligible distance decay λ = 0.01) recover a homogeneous b value distribution, "inconsistent" with high-resolution sampling (e.g., R max = 7.5 km and λ = 0.7 in our study), and thus significant differences in derived probabilities; and (3) the claim that choice of parameters would favor and even artificially create b value anomalies.In our view, the raised criticism neither presents original arguments nor is it critical to the results of the Tormann et al. [2014] study. We first discuss this misconception, and second, we demonstrate one more time that b value anomalies do not result from under sampling. Limited Originality and RelevanceKamer [2014] suggests that the DEW sampling parameter choice (λ) is ambiguous and dependent on the setup of the synthetic test. That is true, of course, and we acknowledge it in our paper (p. 6), but argue based on a sensitivity analysis that our choice of 0.7 is robust and that results do not critically depend on this choice. This is confirmed by both, Kamer's Comment and the additional analysis shown in this Reply. It is fair, of course, to test the sensitivity (as we did also) and try different synthetic structures, and it is equally not surprising that parameters change if the anomaly is removed (case b = 1 in the central volume as studied by Kamer [2014]). It is quite intuitive that without local variation in the data, there is no advantage (but also no disadvantage) in a significant distance weighting. We note that if the central block of the structure is set to b > 1.25 values,...

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Section: Artifacts Caused By Under Sampling?supporting

confidence: 86%

Reply to Comment by Kamer on “Systematic survey of highresolution b value imaging along Californian faults: Inference on asperities”

Tormann

Wiemer

2014

JGR Solid Earth

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“…The effect is significantly enhanced by offsets of the reservoir layer over the fault zone (Mulders, 2003). Studies indicate that the largest impact on shear stresses on a fault results from differential compaction (Roest & Kuilman, 1994;Mulders, 2003;van den Bogert, 2015). As at a certain time these stresses may act on a larger fault area, seismicity could commence at a comparatively high-magnitude level, as is observed at some fields in the Netherlands (Van Eck et al, 2006).…”

Section: Risk Posed By Induced Seismicitymentioning

confidence: 99%

The effect of imposed production measures on gas extraction induced seismic risk

Muntendam-Bos¹,

Roest²,

Waal³

2017

Netherlands Journal of Geosciences

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Shaking and damage in the province of Groningen, the Netherlands, resulting from production-induced seismicity has caused increased public anxiety. Since 2014, production offtake has been reduced stepwise by over 50% in an attempt to minimise production-induced seismicity. The earthquake catalogue, combined with comprehensive data of the changes in production offtake, shows a clear response of seismic activity following the production measures taken. Associated temporal variations in the proportionality between smaller-and larger-magnitude events (the b-value of the Gutenberg-Richter relation) are observed. Since production measures were imposed, the b-value has tended to increase, thus lowering the probability of a larger-magnitude event. The analysis also shows increases in activity rate and b-value prior to larger-magnitude events. Subsequently, the probability of a larger-magnitude event seems to be decreasing prior to the events occurring. This implies that for short-term earthquake prediction of hydrocarbon-production-induced seismicity, these types of analysis could be misleading. However, regional analysis is necessary to explain the observations in terms of rupture initiation. At present, each event felt still draws the interest of both public and press. As some clustering of events in both time and space is still observed, managing both the seismicity and the public perception provides a continuing challenge.

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“…To date, the effect of a mainshock's differential stress change on the subsequent seismicity has not been systematically investigated, but individual case studies suggest that sometimes higher b values are observed after a mainshock (Ogata & Katsura, ; Tamaribuchi et al, ; Tormann et al, , , ; Wiemer et al, ; Wiemer & Katsumata, ). These individual observations highlight the important question of whether such high postmainshock b values are characteristic of aftershock sequences and, if so, whether, when or how they recover.…”

Section: Introductionmentioning

confidence: 99%

The Effect of a Mainshock on the Size Distribution of the Aftershocks

Gulia

Rinaldi

Tormann

et al. 2018

Geophysical Research Letters

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A systematic decay of the aftershock rate over time is one of the most fundamental empirical laws in Earth science. However, the equally fundamental effect of a mainshock on the size distribution of subsequent earthquakes has still not been quantified today and is therefore not used in earthquake hazard assessment. We apply a stacking approach to well‐recorded earthquake sequences to extract this effect. Immediately after a mainshock, the mean size distribution of events, or b value, increases by 20–30%, considerably decreasing the chance of subsequent larger events. This increase is strongest in the immediate vicinity of the mainshock, decreasing rapidly with distance but only gradually over time. We present a model that explains these observations as a consequence of the stress changes in the surrounding area caused by the mainshocks slip. Our results have substantial implications for how seismic risk during earthquake sequences is assessed.

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Earthquake recurrence models fail when earthquakes fail to reset the stress field

Cited by 28 publications

References 23 publications

Reply to Comment by Kamer on “Systematic survey of highresolution b value imaging along Californian faults: Inference on asperities”

Reply to Comment by Kamer on “Systematic survey of highresolution b value imaging along Californian faults: Inference on asperities”

The effect of imposed production measures on gas extraction induced seismic risk

The Effect of a Mainshock on the Size Distribution of the Aftershocks

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