TY - JOUR A1 - Kühn, Daniela A1 - Hainzl, Sebastian A1 - Dahm, Torsten A1 - Richter, Gudrun A1 - Vera Rodriguez, Ismael T1 - A review of source models to further the understanding of the seismicity of the Groningen field JF - Netherlands journal of geosciences : NJG N2 - The occurrence of felt earthquakes due to gas production in Groningen has initiated numerous studies and model attempts to understand and quantify induced seismicity in this region. The whole bandwidth of available models spans the range from fully deterministic models to purely empirical and stochastic models. In this article, we summarise the most important model approaches, describing their main achievements and limitations. In addition, we discuss remaining open questions and potential future directions of development. KW - deterministic KW - empirical KW - hybrid KW - machine learning KW - seismicity model Y1 - 2022 U6 - https://doi.org/10.1017/njg.2022.7 SN - 0016-7746 SN - 1573-9708 VL - 101 PB - Cambridge Univ. Press CY - Cambridge ER - TY - JOUR A1 - Eibl, Eva P. S. A1 - Hainzl, Sebastian A1 - Vesely, Nele I. K. A1 - Walter, Thomas R. A1 - Jousset, Philippe A1 - Hersir, Gylfi Pall A1 - Dahm, Torsten T1 - Eruption interval monitoring at strokkur Geyser, Iceland JF - Geophysical research letters N2 - Geysers are hot springs whose frequency of water eruptions remain poorly understood. We set up a local broadband seismic network for 1 year at Strokkur geyser, Iceland, and developed an unprecedented catalog of 73,466 eruptions. We detected 50,135 single eruptions but find that the geyser is also characterized by sets of up to six eruptions in quick succession. The number of single to sextuple eruptions exponentially decreased, while the mean waiting time after an eruption linearly increased (3.7 to 16.4 min). While secondary eruptions within double to sextuple eruptions have a smaller mean seismic amplitude, the amplitude of the first eruption is comparable for all eruption types. We statistically model the eruption frequency assuming discharges proportional to the eruption multiplicity and a constant probability for subsequent events within a multituple eruption. The waiting time after an eruption is predictable but not the type or amplitude of the next one.
Plain Language Summary Geysers are springs that often erupt in hot water fountains. They erupt more often than volcanoes but are quite similar. Nevertheless, it is poorly understood how often volcanoes and also geysers erupt. We created a list of 73,466 eruption times of Strokkur geyser, Iceland, from 1 year of seismic data. The geyser erupted one to six times in quick succession. We found 50,135 single eruptions but only 1 sextuple eruption, while the mean waiting time increased from 3.7 min after single eruptions to 16.4 min after sextuple eruptions. Mean amplitudes of each eruption type were higher for single eruptions, but all first eruptions in a succession were similar in height. Assuming a constant heat inflow at depth, we can predict the waiting time after an eruption but not the type or amplitude of the next one. Y1 - 2019 U6 - https://doi.org/10.1029/2019GL085266 SN - 0094-8276 SN - 1944-8007 VL - 47 IS - 1 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Sudibyo, Maria R. P. A1 - Eibl, Eva P. S. A1 - Hainzl, Sebastian A1 - Hersir, Gylfi Páll T1 - Eruption Forecasting of Strokkur Geyser, Iceland, Using Permutation Entropy JF - Journal of geophysical research : Solid earth N2 - A volcanic eruption is usually preceded by seismic precursors, but their interpretation and use for forecasting the eruption onset time remain a challenge. A part of the eruptive processes in open conduits of volcanoes may be similar to those encountered in geysers. Since geysers erupt more often, they are useful sites for testing new forecasting methods. We tested the application of Permutation Entropy (PE) as a robust method to assess the complexity in seismic recordings of the Strokkur geyser, Iceland. Strokkur features several minute-long eruptive cycles, enabling us to verify in 63 recorded cycles whether PE behaves consistently from one eruption to the next one. We performed synthetic tests to understand the effect of different parameter settings in the PE calculation. Our application to Strokkur shows a distinct, repeating PE pattern consistent with previously identified phases in the eruptive cycle. We find a systematic increase in PE within the last 15 s before the eruption, indicating that an eruption will occur. We quantified the predictive power of PE, showing that PE performs better than seismic signal strength or quiescence when it comes to forecasting eruptions. KW - permutation entropy KW - forecasting KW - geyser KW - eruption KW - hydrothermal system; KW - volcano-seismology Y1 - 2022 U6 - https://doi.org/10.1029/2022JB024840 SN - 2169-9313 SN - 2169-9356 VL - 127 IS - 10 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Richter, Gudrun A1 - Hainzl, Sebastian A1 - Dahm, Torsten A1 - Zöller, Gert T1 - Stress-based, statistical modeling of the induced seismicity at the Groningen gas field BT - the Netherlands JF - Environmental earth sciences N2 - Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity. KW - induced seismicity KW - modeling KW - statistical seismology KW - forecast Y1 - 2020 U6 - https://doi.org/10.1007/s12665-020-08941-4 SN - 1866-6280 SN - 1866-6299 VL - 79 IS - 11 PB - Springer CY - New York ER - TY - JOUR A1 - Zöller, Gert A1 - Hainzl, Sebastian A1 - Tilmann, Frederik A1 - Woith, Heiko A1 - Dahm, Torsten T1 - Comment on: Wikelski, Martin; Müller, Uschi; Scocco, Paola; Catorci, Andrea; Desinov, Lev V.; Belyaev, Mikhail Y.; Keim, Daniel A.; Pohlmeier, Winfried; Fechteler, Gerhard; Mai, Martin P. : Potential short-term earthquake forecasting by farm animal monitoring. - Ethology. - 126 (2020), 9. - S. 931 - 941. -ISSN 0179-1613. - eISSN 1439-0310. - doi 10.1111/eth.13078 JF - Ethology N2 - Based on an analysis of continuous monitoring of farm animal behavior in the region of the 2016 M6.6 Norcia earthquake in Italy, Wikelski et al., 2020; (Seismol Res Lett, 89, 2020, 1238) conclude that animal activity can be anticipated with subsequent seismic activity and that this finding might help to design a "short-term earthquake forecasting method." We show that this result is based on an incomplete analysis and misleading interpretations. Applying state-of-the-art methods of statistics, we demonstrate that the proposed anticipatory patterns cannot be distinguished from random patterns, and consequently, the observed anomalies in animal activity do not have any forecasting power. KW - animal behavior KW - earthquake precursor KW - error diagram KW - prediction KW - randomness KW - statistics Y1 - 2020 U6 - https://doi.org/10.1111/eth.13105 SN - 0179-1613 SN - 1439-0310 VL - 127 IS - 3 SP - 302 EP - 306 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Sharma, Shubham A1 - Hainzl, Sebastian A1 - Zöller, Gert A1 - Holschneider, Matthias T1 - Is Coulomb stress the best choice for aftershock forecasting? JF - Journal of geophysical research : Solid earth N2 - The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance-slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half-space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half-space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance-slip probabilistic model. Y1 - 2020 U6 - https://doi.org/10.1029/2020JB019553 SN - 2169-9313 SN - 2169-9356 VL - 125 IS - 9 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Fiedler, Bernhard A1 - Zöller, Gert A1 - Holschneider, Matthias A1 - Hainzl, Sebastian T1 - Multiple Change-Point Detection in Spatiotemporal Seismicity Data JF - Bulletin of the Seismological Society of America N2 - Earthquake rates are driven by tectonic stress buildup, earthquake-induced stress changes, and transient aseismic processes. Although the origin of the first two sources is known, transient aseismic processes are more difficult to detect. However, the knowledge of the associated changes of the earthquake activity is of great interest, because it might help identify natural aseismic deformation patterns such as slow-slip events, as well as the occurrence of induced seismicity related to human activities. For this goal, we develop a Bayesian approach to identify change-points in seismicity data automatically. Using the Bayes factor, we select a suitable model, estimate possible change-points, and we additionally use a likelihood ratio test to calculate the significance of the change of the intensity. The approach is extended to spatiotemporal data to detect the area in which the changes occur. The method is first applied to synthetic data showing its capability to detect real change-points. Finally, we apply this approach to observational data from Oklahoma and observe statistical significant changes of seismicity in space and time. Y1 - 2018 U6 - https://doi.org/10.1785/0120170236 SN - 0037-1106 SN - 1943-3573 VL - 108 IS - 3A SP - 1147 EP - 1159 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Woith, Heiko A1 - Petersen, Gesa Maria A1 - Hainzl, Sebastian A1 - Dahm, Torsten T1 - Review: Can Animals Predict Earthquakes? JF - Bulletin of the Seismological Society of America N2 - In public perception, abnormal animal behavior is widely assumed to be a potential earthquake precursor, in strong contrast to the viewpoint in natural sciences. Proponents of earthquake prediction via animals claim that animals feel and react abnormally to small changes in environmental and physico-chemical parameters related to the earthquake preparation process. In seismology, however, observational evidence for changes of physical parameters before earthquakes is very weak. In this study, we reviewed 180 publications regarding abnormal animal behavior before earthquakes and analyze and discuss them with respect to (1) magnitude-distance relations, (2) foreshock activity, and (3) the quality and length of the published observations. More than 700 records of claimed animal precursors related to 160 earthquakes are reviewed with unusual behavior of more than 130 species. The precursor time ranges from months to seconds prior to the earthquakes, and the distances from a few to hundreds of kilometers. However, only 14 time series were published, whereas all other records are single observations. The time series are often short (the longest is 1 yr), or only small excerpts of the full data set are shown. The probability density of foreshocks and the occurrence of animal precursors are strikingly similar, suggesting that at least parts of the reported animal precursors are in fact related to foreshocks. Another major difficulty for a systematic and statistical analysis is the high diversity of data, which are often only anecdotal and retrospective. The study clearly demonstrates strong weaknesses or even deficits in many of the published reports on possible abnormal animal behavior. To improve the research on precursors, we suggest a scheme of yes and no questions to be assessed to ensure the quality of such claims. Y1 - 2018 U6 - https://doi.org/10.1785/0120170313 SN - 0037-1106 SN - 1943-3573 VL - 108 IS - 3A SP - 1031 EP - 1045 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Fiedler, Bernhard A1 - Hainzl, Sebastian A1 - Zöller, Gert A1 - Holschneider, Matthias T1 - Detection of Gutenberg-Richter b-Value Changes in Earthquake Time Series JF - Bulletin of the Seismological Society of America N2 - The Gutenberg-Richter relation for earthquake magnitudes is the most famous empirical law in seismology. It states that the frequency of earthquake magnitudes follows an exponential distribution; this has been found to be a robust feature of seismicity above the completeness magnitude, and it is independent of whether global, regional, or local seismicity is analyzed. However, the exponent b of the distribution varies significantly in space and time, which is important for process understanding and seismic hazard assessment; this is particularly true because of the fact that the Gutenberg-Richter b-value acts as a proxy for the stress state and quantifies the ratio of large-to-small earthquakes. In our work, we focus on the automatic detection of statistically significant temporal changes of the b-value in seismicity data. In our approach, we use Bayes factors for model selection and estimate multiple change-points of the frequency-magnitude distribution in time. The method is first applied to synthetic data, showing its capability to detect change-points as function of the size of the sample and the b-value contrast. Finally, we apply this approach to examples of observational data sets for which b-value changes have previously been stated. Our analysis of foreshock and after-shock sequences related to mainshocks, as well as earthquake swarms, shows that only a portion of the b-value changes is statistically significant. Y1 - 2018 U6 - https://doi.org/10.1785/0120180091 SN - 0037-1106 SN - 1943-3573 VL - 108 IS - 5A SP - 2778 EP - 2787 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Pirli, Myrto A1 - Hainzl, Sebastian A1 - Schweitzer, Johannes A1 - Köhler, Andreas A1 - Dahm, Torsten T1 - Localised thickening and grounding of an Antarctic ice shelf from tidal triggering and sizing of cryoseismicity JF - Earth & planetary science letters N2 - We observe remarkably periodic patterns of seismicity rates and magnitudes at the Fimbul Ice Shelf, East Antarctica, correlating with the cycles of the ocean tide. Our analysis covers 19 years of continuous seismic recordings from Antarctic broadband stations. Seismicity commences abruptly during austral summer 2011 at a location near the ocean front in a shallow water region. Dozens of highly repetitive events occur in semi-diurnal cycles, with magnitudes and rates fluctuating steadily with the tide. In contrast to the common unpredictability of earthquake magnitudes, the event magnitudes show deterministic trends within single cycles and strong correlations with spring tides and tide height. The events occur quasi-periodically and the highly constrained event sources migrate landwards during rising tide. We show that a simple, mechanical model can explain most of the observations. Our model assumes stick-slip motion on a patch of grounded ice shelf, which is forced by the variations of the ocean-tide height and ice flow. The well fitted observations give new insights into the general process of frictional triggering of earthquakes, while providing independent evidence of variations in ice shelf thickness and grounding. KW - tidally modulated cryogenic seismicity KW - stick-slip motion KW - event recurrence predictability KW - ice-shelf thickness KW - ice-shelf grounding KW - East Antarctica Y1 - 2018 U6 - https://doi.org/10.1016/j.epsl.2018.09.024 SN - 0012-821X SN - 1385-013X VL - 503 SP - 78 EP - 87 PB - Elsevier CY - Amsterdam ER -