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Earthquake engineering normally describes earthquake activity as a Poissonian process. This approximation is simple, but not entirely satisfactory. In this paper, a method for evaluating the non-Poissonian occurrence probability of seismic events, through empirical survival probability functions, is proposed. This method takes into account the previous history of the system. It seems robust enough to be applied to scant datasets, such as the Italian historical earthquake catalog, comprising 64 events with M &ge, 6.00 since 1600. The requirements to apply this method are (1) an acceptable knowledge of the event rate, and (2) the timing of the last two events with magnitude above the required threshold. I also show that it is necessary to consider all the events available, which means that de-clustering is not acceptable. Whenever applied, the method yields a time-varying probability of occurrence in the area of interest. Real cases in Italy show that large events obviously tend to occur in periods of higher probability.

This research demonstrates the utilization of spatial arrangement investigation methods for earthquake series generated along Chaman Fault in Balochistan region to put an effort to identify clusters, discover local and global spatial configurations for the incident of earthquakes occurred from 1900 to 2017 with geographical information system (GIS). The preferred method in this research was global Moran’s I, Getis–Ord Gi*, quadrant count analysis, Getis–Ord general G, kernel density estimation, average nearest neighbor, Anselin Local Moran’s I and geographical coverage of the data. Each method was executed in the GIS, so that calculations could be conceded out rapidly and proficiently. Outcomes exhibited that such methods are proficient of identifying clusters in the spatial configurations of earthquakes. Both local and global spatial statistics suggested that earthquakes are populated in the northern Balochistan where the Chaman Fault bends and have higher seismicity. This study also reveals that earthquakes with higher magnitudes are particularly intense in the north Balochistan region where earthquake activities are utmost active along Chaman Fault. Lastly this study also shows that earthquakes having moderate magnitudes were predominantly rigorous in southern Balochistan because the region is formed from continental rifting giving no recognizable spreading centers of earthquakes. We conclude from this research that the pattern investigation methods applied earthquake catalog in Balochistan province along Chaman fault could spot clusters from the events of earthquakes.

An earthquake is the vibration pattern of the Earth’s crust induced by the sliding of geological faults. They are usually recorded for later studies. However, strong earthquakes are rare, small-magnitude events may pass unnoticed and monitoring networks are limited in number and efficiency. Thus, earthquake catalog are incomplete and scarce, and researchers have developed simulators of such catalogs. In this work, we start from synthetic catalogs generated with the TREMOL-3D software. TREMOL-3D is a stochastic-based method to produce earthquake catalogs with different statistical patterns, depending on certain input parameters that mimics physical parameters. When an appropriate set of parameters are used, TREMOL-3D could generate synthetic catalogs with similar statistical properties observed in real catalogs. However, because of the size of the parameter space, a manual searching becomes unbearable. Therefore, aiming at increasing the efficiency of the parameter search, we here implement a Machine Learning approach based on Random Forest classification, for an automatic parameter screening. It has been implemented using the machine learning Python’s library SciKit Learn. This work is partially supported by the Spanish Ministry of Economy and Competitivity under contract TIN2015-65316-P and by the Catalan Government through the programmes 2017-SGR-1414, 2017-SGR-962 and the RIS3CAT DRAC project 001-P-001723. Moreover, this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 777778 (MATHROCKS). The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under the ChEESE project, grant agreement No. 823844.

We apply a template matching detection to report a swarm-like foreshock sequence concentrated near the northern edge of the strike-slip fault rupture of the 25 September 2019 MW 6.5 Ambon earthquake in Seram, Indonesia. The template matching helps to identify small earthquakes that the routine earthquake catalog has not listed. The magnitude of completeness decreases from 3.1 (Badan Meteorologi Klimatologi dan Geofisika – BMKG catalog) to 1.7 in the improved catalog. We detect 3201 foreshocks which are tens fold the number of foreshocks in the routine earthquake catalog. We did not find a significant temporal variation in the b-value of the frequency–magnitude distribution (FMD) of the foreshock seismicity prior to initiating the dynamic rupture of the mainshock. The foreshocks around the mainshock hypocenter start to be busy since the beginning of July 2019 and continuously accelerates, with a minor variation in the seismicity rates and b-values. Although possible, we did not suggest that the stochastic cascade effect plays a role in the mainshock nucleation process. We discuss and highlight the possibility of fluid triggering to explain the high b-values of foreshock seismicity.

The main goal of this article is to decluster Iranian plateau seismic catalog by the epidemic-type aftershock sequence (ETAS) model and compare the results with some older methods. For this purpose, Iranian plateau bounded in 24°–42°N and 43°–66°E is subdivided into three major tectonic zones: (1) North of Iran (2) Zagros (3) East of Iran. The extracted earthquake catalog had a total of 6034 earthquakes (Mw > 4) in the time span 1983–2017. The ETAS model is an accepted stochastic approach for seismic evaluation and declustering earthquake catalogs. However, this model has not yet been used to decluster the seismic catalog of Iran. Until now, traditional methods like the Gardner and Knopoff space–time window method and the Reasenberg link-based method have been used in most studies for declustering Iran earthquake catalog. Finally, the results of declustering by the ETAS model are compared with result of Gardner and Knopoff (Bull Seismol Soc Am 64(5):1363–1367, 1974), Uhrhammer (Earthq Notes 57(1):21, 1986), Gruenthal (pers. comm.) and Reasenberg (Geophys Res 90:5479–5495, 1985) declustering methods. The overall conclusion is difficult, but the results confirm the high ability of the ETAS model for declustering Iranian earthquake catalog. Use of the ETAS model is still in its early steps in Iranian seismological researches, and more parametric studies are needed.

In 1972, V. Keilis-Borok and I. Gelfand introduced the phenomenological approach based on the morphostructural zoning and pattern recognition for identification of earthquake-prone areas. This methodology identifies seismogenic nodes capable of generating strong earthquakes on the basis of geological, morphological, and geophysical data, which do not contain information on past seismicity. In the period 1972–2018, totally, 26 worldwide seismic regions have been studied and maps showing the recognized earthquake-prone areas in each region have been published. After that, 11 of these regions were hit by earthquakes of the relevant sizes. The goal of this work is to analyze the correlation of the post-publication events with seismogenic nodes defined in these 11 regions. The test was performed using the NEIC earthquake catalog because it uniformly defines the location and magnitudes of earthquakes over the globe. The ArcMap facilities were exploited to plot the post-publication events on the maps showing the recognized seismogenic nodes. We found that about 86% of such events fall in the recognized seismogenic nodes. The performed test proved the sufficient validity of the methodology for identifying areas capable of strong earthquakes and confirms the idea on nucleating strong earthquakes at the nodes.

By a systematic mapping of the b-value along profiles perpendicular to the Mexican Wadati-Benioff zone, we obtained important characteristics pertaining the stress state and faulting style related to the subduction process. To this purpose, we used data from the earthquake catalog reported by the Servicio Sismologico Nacional (1988–2016). We investigate depth variations of the b-value for the Cocos and Rivera under North American plates interface, by a detailed analysis of 15 cross-sections. The obtained b-value profiles vary from 0.50 to 2.50, which nevertheless appear related to the faulting style and stress state. By comparing the locations and focal mechanism of the largest events with the b-values of the surrounding regions, our analysis corroborates the dependence of the b-value on the faulting style. Thrust events occur in regions of low and high b-value at depths 30 km), in agreement with global studies. These results support the hypothesis that differential stress processes may be behind the occurrence of the different faulting style. On the contrary, by analyzing the mean b-values for both types of faulting mechanism at each of the cross-sections, we found a significantly lower mean b-value related to normal faulting for those regions where the 8 (Mw 8.2) and 19 (Mw 7.1) September 2017 earthquakes occur. These results lead us to conclude that those regions experienced an increased stress state prone to the occurrence of normal-intraplate events. We also compare the b-value distribution with Vp and Q tomography studies obtaining a good correlation between them. We found evidence to relate b-value variations with subduction processes such as stress state due to tectonic and flexural conditions, and to a lesser extent to material heterogeneity and fluid dehydration.

We investigated the foreshock activity characteristics using the Japan Meteorological Agency Unified Earthquake Catalog for the last 20 years. Using the nearest-neighbor distance approach, we systematically and objectively classified the earthquakes into clustered and background seismicity. We further categorized the clustered events into foreshocks, mainshocks, and aftershocks and analyzed their statistical features such as the b-value of the frequency–magnitude distribution. We found that the b-values of the foreshocks are lower than those of the aftershocks. This b-value difference suggested that not only the stochastic cascade effect but also the stress changes/aseismic processes may contribute to the mainshock-triggering process. However, forecasting the mainshock based on b-value analysis may be difficult. In addition, the rate of foreshock occurrence in all clusters (with two or more events) was nearly constant (30–40%) over a wide magnitude range. The difference in the magnitude, time, and epicentral distance between the mainshock and largest foreshock followed a power law. We inferred that the distinctive characteristics of foreshocks can be better revealed using the improved catalog, which includes the micro-earthquake information.

In this study, an effort has been made to perform seismic hazard analysis (SHA) for the state of Assam, considering earthquake catalog collected since 1761–2015 using PSHA and DSHA methods at bed r...

Before the ML 6.6 Meinong earthquake in 2016, intermediate-term quiescence (Qi), foreshocks, and short-term quiescence (Qs) were extracted from a comprehensive earthquake catalog. In practice, these behaviors are thought to be the seismic indicators of an earthquake precursor, and their spatiotemporal characteristics may be associated with location, magnitude, and occurrence time of the following main shock. Hence, detailed examinations were carried out to derive the spatiotemporal characteristics of these meaningful seismic behaviors. First, the spatial range of the Qi that occurred for ~ 96 days was revealed in and around the Meinong earthquake. Second, a series of foreshocks was present for ~ 1 day, clustered at the southeastern end of the Meinong earthquake. Third, Qs was present for ~ 3 days and was pronounced after the foreshocks. Although these behaviors were recorded difficultly because the Qi was characterized by microseismicity at the lower cut-off magnitude, between ML 1.2 and 1.6, and most of the foreshocks were comprised of earthquakes with a magnitude lower than 1.8, they carried meaningful precursory indicators preceding the Meinong earthquake. These indicators provide the information of (1) the hypocenter, which was indicated by the area including the Qi, foreshocks, and Qs; (2) the magnitude, which could be associated to the spatial range of the Qi; (3) the asperity locations, which might be related to the areas of extraordinary low seismicity; and (4) a short-term warning leading of ~ 3 days, which could have been announced based on the occurrence of the Qs. Particularly, Qi also appeared before strong inland earthquakes so that Qi might be an anticipative phenomenon before a strong earthquake in Taiwan.

Two new estimators of parameters λ0and β of the Gutenberg-Richter seismicity relation are presented for the case in which several complete portions of an earthquake catalog are used in the estimation process. These estimators are the ones that maximize the joint likelihood of both parameters, considering Poisson arrivals. Therefore, as shown in this paper, they are more robust than estimators previously presented in the literature. The numerical effort to compute the new estimators is greater than with previously published formulas because the new method requires solution of an implicit algebraic equation, for which we provide an iteration strategy of fast convergence. In our opinion, the extra effort is warranted in view of the usual scarcity of data and in view of the extra precision that the new method brings.

Data on rock falls and landslides caused by strong earthquakes in the Zhetysu Alatau, Ile Alatau, Kungei Alatau and Teriskei Alatau mountain ranges on the territory of Southeastern Kazakhstan are presented. The study revealed more than 60 large seismogenic rock falls and landslides, the volume of 25 of them varies from 10 to 100 mil. m3, and the volume of the four largest exceeds 100 mil. m3. The volume of the largest rock fall in the valley of the Ulken Almaty river in the Ile Alatau mountain range is estimated at 380 mil. m3. The highest density of seismogenic landslides was recorded in the low-mountain zone of the northern slope of the Ile Alatau range where the magnitude 9 earthquake of 1887 caused a massive formation of landslides with the volume totaling more than 400 mil. m3 and a density of 1/5 km2. The proportion of landslide-affected areas is estimated at 5% of the area of their occurrence. In the mid- and high-mountain zones of Zhetysu, Ile and Kungei Alatau, the density of seismogenic rock falls varies from 1/100 to 1/50 km2, and the proportion of rock fall-affected areas varies from 1 to 1.5%. It is found that seismogenic rock falls have dammed 26 lakes, and the volume of nine such lakes exceeds 10 mil. m3. The largest rock fall-affected lakes is Upper Zhasylkol in the valley of the Aganakty river in Zhetysu Alatau with the volume of 44 mil. m3. Data from earthquake catalog were used to compile the map for the recurrence frequency of earthquakes of magnitude higher than 6, capable of causing seismogenic rock falls and landslides. It is found that during the last 130 years, in Ile and Kungei Alatau such earthquakes recurred four times. It is established that earthquakes with maximum magnitude 9 are possible in the mountainous regions of Southeastern Kazakhstan.

To rapidly estimate fatalities following an earthquake and provide adequate emergency response and medical rescue, a suitable model should be developed according to local data and physical conditions. Mainland China is divided into five regions based on the regionalization of tectonic background, seismic activity, and development level. This study develops several earthquake fatality ratio estimation models for different regions using 377 earthquake fatalities and population exposure data from 1951 to 2018 provided by the Mainland China Composite Damaging Earthquake Catalog. The earthquake fatality records are normalized by the Human Development Index to the year 2018 level. Because the fatality records of a few catastrophic events have a negative impact on the regression results of all events, we also develop fatality ratio estimation models, especially for catastrophic earthquakes. Furthermore, we use the recorded fatalities of two example periods to verify the applicability of the fatality ratio estimation models. The results show that more than 85% of estimations are within one order of magnitude compared to the records. Finally, based on the verified model and the normal cumulative distribution method, we also try to determine the earthquake emergency response level. We then perform a rapid estimation of fatalities for the 2019 Changning Ms 5.8 earthquake, obtaining an expected result. The applicability of the proposed model to post-earthquake rapid fatality estimation and disaster assessment of earthquake scenarios is expected to play an important role in future earthquake relief planning and post-earthquake rapid emergency response of the Chinese government.

Costa Rica is a seismically active region located in a subduction zone. Combining earthquake data from the National Seismological Network and several Central American catalogs from 1522 to 2020, we present a new estimation for the Gutenberg-Richter relationship. The seismic catalog compiled with ~122,000 earthquakes was studied by calculating the magnitude of completeness (Mc) and by applying a space-time window declustering method. The residual catalog and a previously proposed seismic zonation were used to determine the b-value, the maximum magnitude (Mmax), and the mean recurrence interval (MRI). Our results show a temporal and geographic variation in the Mc, decreasing from 7.0 since 1793 to 3.0 since 1995, and with the lowest estimate (2.5) in Central Costa Rica. The b-values of 0.85 for the entire catalog and ~0.83 for the interplate zones, are similar to other regions worldwide with young subducting slabs. There is a general trend of higher and more variable b-values among the upper-plate (average 0.90) and intraslab (1.14) zones as compared to the interplate regions (0.85). The upper-plate variability is explained in terms of the diversity in geological units and faulting style, whereas in the interplate and the subducting slab is connected to the stress level imposed by different seafloor morphologies and hydration states along the margin. Our data suggest a seismic potential of moment magnitude (Mw) 7.9–8.0 for the Nicoya and Southern Nicaragua interplate zones and for the Limon region. The Gutenberg-Richter distribution shows that a Mw 7.0 has a longer MRI for the intraslab zones (~72 years) than for the subduction interplate region (~15 years) and plate and microplate boundaries (~40–45 years). Interplate earthquakes have occurred recently (1991 Mw 7.7 and 2012 Mw 7.6) but no major intraslab since 1948 (Mw 7.0). Universidad de Costa Rica/[731-B9-780]/UCR/Costa Rica Universidad de Costa Rica/[113-B5-704]/UCR/Costa Rica Universidad de Costa Rica/[113-B9-911]/UCR/Costa Rica UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela Centroamericana de Geología

We studied spatial and temporal variations in the b-value to investigate volcanic processes at Popocatepetl volcano, Central Mexico. For this purpose, we used data from the earthquake catalog compiled by the Centro Nacional de Prevencion de Desastres from 1995 to 2021. Significant variations in the b-value are detected, with b-value ranging from 0.52 to 2.9. We mapped two seismic clusters, the first one below the crater and the second one southeast of the summit region. High b-value volumes are located beneath the volcano. These volumes are located at the following depth intervals of 4 km a.s.l – 2 km b.s.l and 3 km a.s.l – 2 km b.s.l. The statistical tests showed that the selected low and high b-value regions are significant at a 99% confidence level. By comparing the earthquake locations and available focal mechanisms with the b-values, our analysis suggests no clear dependence of the b-values on the faulting style. We also compare the b-value distributions with seismic wave tomography studies obtaining a good correlation between the b-value mapped zones and low-velocity regions. We found evidence to relate high b-value anomalies with regions of high crack density and/or high pore pressure associated with the location of nearby magma bodies. Our interpretation is supported by geophysical evidence from seismic wave tomography.

Due to the initiation of the Hellenic Unified Seismic Network (HUSN) in late 2007, the quality of observation significantly improved by 2011. For example, the representative magnitude level considerably has decreased and the number of annually recorded events has increased. The new observational system highly expanded the possibilities for studying regularities in seismicity. In view of this, the authors revisited their studies of the diurnal periodicity of representative earthquakes in Greece that was revealed earlier in the earthquake catalog before 2011. We use 18 samples of earthquakes of different magnitudes taken from the catalog of Greek earthquakes from 2011 to June 2016 to derive a series of the number of earthquakes for each of them and calculate its average diurnal course. To increase the reliability of the results, we compared the data for two regions. With a high degree of statistical significance, we have obtained that no diurnal periodicity can be found for strongly representative earthquakes. This finding differs from the estimates obtained earlier from an analysis of the catalog of earthquakes at the same area for 1995–2004 and 2005–2010, i.e., before the initiation of the Hellenic Unified Seismic Network. The new results are consistent with the hypothesis of noise discrimination (observational selection) explaining the cause of the diurnal variation of earthquakes with different sensitivity of the seismic network in daytime and nighttime periods.

In this paper, the following seismic parameters, the maximum recorded magnitude ( $$M_{max})$$ , the Gutenberg–Ritcher b-value and the (normalized) mean seismic activity rate, AR, have been calculated for the Iberian Peninsula and surroundings. A geographic information system has been employed to compile all data, to work with different geographic systems and to generate the maps. An improved version of the National Geographic Institute of Spain earthquake catalog has been considered as input. Due to the detection network evolution and the extent of the territory, completeness values must be sectored to obtain reliable b-values and AR values. So, a previous work on regionalization has been considered. First, a working catalog has been elaborated. To do so, the size of some shocks through specific studies have been reviewed, magnitudes have been converted to moment magnitude ( $$M_{w})$$ and dependent events have been removed. Second, for the b-value and the AR calculation a method that considers inhomogeneous catalogs, different magnitudes and various years of completeness has been employed. Also, different decluster parameters and various minimum number of events have been considered. Finally, to represent the values, a multi-resolution grid $$(0.5^{{{\circ }}}\times 0.5^{{{\circ }}}$$ , $$1^{{{\circ }}}\times 1^{{{\circ }}}$$ and $$2^{{{\circ }}}\times 2^{{{\circ }}})$$ has been deployed. The pictures obtained show the seismicity in the terms of size, stress-meter and frequency. The highest $$M_{max}$$ has been obtained in the SW of the Iberian Peninsula with a marine epicenter. Regarding the b-value, in the contact boundary between the Africa and Eurasian plates this value is around 1.0 or minor. Contrariwise, in the mainland, values higher than 1.2 are predominant. Finally, the highest AR values are found in the SE of the Iberian Peninsula and remarkable values are also present in the NE.

To study the prospective areas of upcoming strong-to-major earthquakes, i.e., M w ≥ 6.0, a catalog of seismicity in the vicinity of the Thailand-Laos-Myanmar border region was generated and then investigated statistically. Based on the successful investigations of previous works, the seismicity rate change (Z value) technique was applied in this study. According to the completeness earthquake dataset, eight available case studies of strong-to-major earthquakes were investigated retrospectively. After iterative tests of the characteristic parameters concerning the number of earthquakes (N) and time window (T w ), the values of 50 and 1.2 years, respectively, were found to reveal an anomalous high Z-value peak (seismic quiescence) prior to the occurrence of six out of the eight major earthquake events studied. In addition, the location of the Z-value anomalies conformed fairly well to the epicenters of those earthquakes. Based on the investigation of correlation coefficient and the stochastic test of the Z values, the parameters used here (N = 50 events and T w = 1.2 years) were suitable to determine the precursory Z value and not random phenomena. The Z values of this study and the frequency-magnitude distribution b values of a previous work both highlighted the same prospective areas that might generate an upcoming major earthquake: (i) some areas in the northern part of Laos and (ii) the eastern part of Myanmar.

The daily periodicity in four regions of the Dushanbe–Vakhsh area is analyzed. The study considers representative, nonrepresentative, and intermediate-energy earthquakes. Analysis of the specific features of the shape of the diurnal variation on workdays and weekends make it possible (1) to reliably conclude that the anomalous daily variation on workdays in medium-energy earthquake samplings is of technogenic origin and (2) suggest similarities in samplings of the weakest and strongest earthquakes. Apparently, the catalog includes a large number of industrial blasts. The number of blasts in earthquake samplings of various epochs and energies is estimated.

Probabilistic seismic hazard analysis (PSHA) generally requires the identification of line sources (active faults) and area sources where seismicity parameters must be determined. It is not easy to identify seismic sources and to estimate seismicity parameters for sources in the intraplate region. We perform an alternative PSHA with a synthetic earthquake catalog, which does not require the delineation of seismic sources. A synthetic catalog of the Korean Peninsula for 500,000 years is constructed by simulating earthquakes using the Monte Carlo method in such a way that an earthquake is randomly selected from the observed earthquake catalog, its epicenter is perturbed by a normally distributed random number, and a magnitude is assigned to the simulated event with a random value generated based on the Gutenberg-Richter magnitude-frequency relation with specified minimum and maximum magnitudes. The seismicity of the Korean Peninsula is thoroughly investigated for estimation of parameters required for synthesizing the catalog. The SMSIM computer program is used to simulate ground motions at sites instead of estimating the ground motion prediction equation. Two sites are chosen for PSHA; the one is the Seoul City Hall site (Seoul site), a densely populated metropolitan site, and the other is the Gyeongju City Hall site (Gyeongju site) close to the epicenter of the M L 5.8 earthquake on 12 September 2016. Seismic hazard curve, uniform hazard spectra (UHSs), and deaggregation of hazard for two sites are presented. The mean return periods for 0.1, 0.2, and 0.3 g at the Seoul site appears to be 1640, 6170, and 17650 years, respectively while those at the Gyeongju site appears to be 327, 1197, and 3548 years, respectively. The mean return periods for the Seoul site are around five times longer than those for the Gyeongju site, and this fact implies that the seismic hazard level of the Gyeongju site is considerably higher than that of the Seoul site. UHSs for 10% and 2% probabilities of exceedance over 50 years are constructed at both sites. The spectra show peak amplifications around the 0.05-s period.

Based on the earthquake catalog data for the Koyna–Warna region of induced seismicity in western India, the seasonal variations in seismic activity associated with annual fluctuations in the reservoir water level are analyzed over the time span of the entire history of seismological observations in this region. The regularities in the time changes in the structure of seasonal variations are revealed. The seasonal seismic activity is minimal in May–June when the reservoir level is lowest. During the remaining part of the year, the activity has three peaks: the fall peak in September, winter peak in November–December, and spring peak in February–March. The first mentioned peak, which falls in the phase of the water level reaching its maximal seasonal value is considered as the immediate response of the fluid saturated medium to the additional loading under the weight of reservoir water. The two subsequent maxima concur with the decline phase in the reservoir level and are interpreted as the delayed response associated with the changes in the properties of the medium due to water diffusion. It is shown that the intensities of the immediate and delayed responses to the seasonal water level variations both vary with time as does their ratio. The probable factors affecting the variations in the intensity of the seasonal components of the reservoir-induced seismicity are discussed.

A comprehensive earthquake catalog was compiled for Iraq and neighboring areas as part of a broader probabilistic seismic‐hazard assessment project. The Iraq Seismic Network (ISN) was established in 1976 and became operational in the early 1980s. However, recording and reporting of seismic data has been intermittent in Iraq. Hence, events were collected from various sources, including the ISN when available, International Seismological Centre (ISC), European‐Mediterranean Seismological Centre, U.S. Geological Survey Centennial Catalog, Global Centroid Moment Tensor solutions, and Ambraseys’ extensive work on cataloging of instrumental era earthquakes in the Middle East (e.g., Ambraseys, 1978, 2001, 2009). We supplement these with new direct moment magnitude calculations based on coda calibration technique. For many of the larger events in the catalog, more than one magnitude is available. Directly calculated moment magnitudes ( M w) were favored, followed by body‐wave magnitude ( m b) obtained from the ISC. Where no directly calculated M w was available, other magnitude scales were converted to M w using relationships compatible with the local catalog. The resulting earthquake catalog spans from the year 1900 until the end of 2009, covers the region bounded by 26°–40° N latitudes and 36°–51° E longitudes, and includes more than 18,000 earthquakes, of which roughly 4000 are M w 4.0 or larger.

We apply a waveform matching technique to obtain a detailed earthquake catalog around the rupture zone of the 5 September 2012 moment magnitude 7.6 Nicoya earthquake, with emphasis on its aftershock sequence. Starting from a preliminary catalog, we relocate ~7900 events using TomoDD to better quantify their spatiotemporal behavior. Relocated aftershocks are mostly clustered in two groups. The first is immediately above the major coseismic slip patch, partially overlapping with shallow afterslip. The second one is 50 km SE to the main shock nucleation point and near the terminus of coseismic rupture, in a zone that exhibited little resolvable afterslip. Using the relocated events as templates, we scan through the continuous recording from 29 June 2012 to 30 December 2012, detecting approximately 17 times more than template events. We find 190 aftershocks in the first half hour following the main shock, mostly along the plate interface. Later events become more scattered in location, showing moderate expansion in both along-trench and downdip directions. From the detected catalog we identify 53 repeating aftershock clusters with mean cross-correlation values larger than 0.9, and indistinguishably intracluster event locations, suggesting slip on the same fault patch. Most repeating clusters occurred within the first major aftershock group. Very few repeating clusters were found in the aftershock grouping along the southern edge of the Peninsula, which is not associated with substantial afterslip. Our observations suggest that loading from nearby afterslip along the plate interface drives spatiotemporal evolution of aftershocks just above the main shock rupture patch, while aftershocks in the SE group are to the SE of the observed updip afterslip and poorly constrained.

Earthquakes can pose a serious threat to people and their environment. Natural earthquakes have the potential to be disastrous and mostly occur unexpectedly. Induced earthquakes caused by anthropogenic activities are commonly less disastrous, but can be a great nuisance and are increasingly attracting public attention. The physical processes behind seismicity are not understood well enough to predict natural earthquakes or to completely control induced earthquakes. Estimates about the future occurrence of earthquakes are typically very uncertain, which makes it difficult to use these estimates for mitigation strategies. These restrictions partially arise from the limited resolution of available data and analyses. This thesis will address these limits two-fold. First, it presents a holistic approach for natural earthquake sequences that translates the typically very low earthquake occurrence probabilities into risk estimates—these might reach intolerable levels and justify mitigation actions; in the broadest sense, these may save lives. Secondly, it presents a fundamental approach to produce a high-resolution earthquake catalog of consistent quality using a sensitive detection method and dedicated post-processing; this approach detects very small earthquakes and offers new possibilities for seismicity analyses. The first contribution in this thesis describes an alternative risk mitigation strategy based on probabilistic risk forecasting and cost–benefit analysis, which can support objective short-term evacuation decisions. We apply this approach to a scenario earthquake sequence that simulated a repeat of the 1356 Basel earthquake (∼Mw6.7), one of the most damaging events in central Europe. Based on this simulated sequence, we explore how to possibly provide decision support and information throughout an earthquake crisis. We forecast earthquake consequences, specifically quantified in terms of human loss. The final cost–benefit analysis adds value beyond making probabilistic forecasts: it provides objective statements that may justify evacuations. Compared to an earlier study, we incorporate recent developments in short-term earthquake forecasting and more detailed settlement data to permit spatial forecasts and district-wise decision-making. These new ingredients permit an increased spatial resolution for the decision support and have the potential to improve the cost-effectiveness of mitigation actions. For instance, the occurrence of an M5.5 earthquake or larger would justify evacuations in the central part of the city of Basel, Switzerland. To deliver such supportive information in a simple form, we propose a warning approach in terms of alarm levels. The second contribution in this thesis describes the development and analysis of a consistent high-resolution earthquake catalog of induced seismicity in the Enhanced Geothermal System (EGS) in Basel. The Basel EGS was a deep geothermal energy project. Seismic monitoring at the Basel EGS site has been running for more than a decade. Yet, the details of the long-term behavior of its induced seismicity remained unexplored because a seismic event catalog that is consistent in resolution and in magnitudes did not exist. Such details are essential for developing guidelines and mitigation strategies on how to safely operate and terminate injection activities. We reinvestigate the induced sequence in detail and search for the smallest earthquakes in the available seismic recordings of the injection and long-term period. We detect these “buried” earthquakes with a sensitive matched filter technique based on cross-correlation. Due to quality deficits in the recordings, we apply advanced techniques, including a machine learning method, to obtain consistency in terms of a high detection sensitivity and robust magnitude estimates. The new catalog contains more than 280 000 earthquakes down to Mw−1.5, which have never been considered before. These events offer a much higher temporal resolution of seismicity and gain new insights into the seismic behavior of the EGS. In the injection period, we resolve temporal variations of seismicity parameters that indicate a hazardous modification of the seismogenic behavior in the EGS. In the long-term period, we find a preferential temporal clustering of earthquakes. We further demonstrate the new capabilities offered by the high-resolution catalog. We find a breakdown in the Gutenberg–Richter scaling during the reservoir stimulation, which we show is partially caused by a method-independent detection limitation during high event rates, and likely has additional physical reasons. This scaling break has implications for the design of advanced mitigation strategies and must be carefully considered in future EGS projects. Further, we already provide insights into the long-term behavior of the induced Basel sequence by investigating the temporal clustering and whether surface waves of remote earthquakes modulate seismicity by dynamic triggering. Our analyses reveal characteristic foreshock activity increases in the earthquake clusters, but no indication for remote dynamic triggering. In summary, this thesis contributes novel approaches to seismological research, pro- vides useful input for further studies, and may stimulate discussions among researchers, decisions makers, and the public. The individual contributions of this thesis improve specific aspects of seismic risk assessment and could eventually facilitate the reduction of seismic risk. The first contribution gives an idea of the decision support that can be currently provided by research and may specifically raise awareness of the omnipresent seismic risk in Basel; it could lay the groundwork to inform the public about their own current seismic risk level. The second contribution will give the opportunity to study the sequence in unprecedented detail and resolution, which might help to better understand the physical processes in a deep geothermal reservoir. These insights may improve the way in which deep geothermal projects are brought to success, for example, by better evaluating reservoir creation to guarantee safety for society. The presented method to produce consistent high-resolution catalogs may facilitate better-calibrated seismicity forecasting models and to simultaneously forecast more timely. Viewed optimistically, both contributions of this thesis combined facilitate a new compelling pursuit: a more accurate and timely short-term risk assessment to further improve decision support.

The present work aims at establishing an earthquake catalog for seismic hazard assessment in Lebanon. This catalog includes two different parts: historical earthquakes and instrumental earthquakes. The first part of the article describes the work done on the period 31 B.C.E. to the end of the nineteenth century. Numerous studies published in the last 30 yr, devoted to preinstrumental earthquakes in Lebanon, had not been included in any parametric earthquake catalog. A thorough and critical review of these studies was devised to check their respective interpretations of available earthquake records in terms of seismic parameters (date, location, and size) and to select for each earthquake the most reliable interpretation. The second part provides the details on the selection of instrumental solutions for the period 1900–2015 and for magnitudes≥4. From global instrumental earthquake catalogs, we build a unified earthquake catalog for Lebanon and bordering regions. A selection scheme is applied for the choice of the best location and the best magnitude among solutions available. The number of events in the catalog is relatively small, and all earthquakes can be checked one by one. The earthquake catalog is homogenized in moment magnitude. For 89% of the events, an Mw proxy was calculated from the original magnitude, applying conversion equations. The merging of the historical and instrumental periods highlights a specificity of this zone: the instrumental seismicity (1900–2015) corresponds to a relatively quiet period for Lebanon. The historical part, covering 2000 yr, includes similar periods of quiescence, as well as much more active periods with destructive earthquakes.

Seismogenic source zone models, including the delineation and the characterization, still have a role to play in seismic hazard calculations, particularly in regions with moderate or low to moderate seismicity. Seismic source zones establish areas with common tectonic and seismic characteristics, described by a unique magnitude–frequency distribution. Their definition can be addressed from different views. Traditionally, the source zones have been geographically outlined from seismotectonic, geological structures, and earthquake catalogs. Geographic information systems (GIS) can be of great help in their definition, as they deal rigorously and less ambiguously with the available geographical data. Moreover, novel computer science approaches are now being employed in their definition. The Pyrenees mountain range – in southwest Europe – is located in a region characterized by low to moderate seismicity. In this study, a method based purely on seismic catalogs, managed with a GIS and a triclustering algorithm, were used to delineate seismogenic zones in the Pyrenees. Based on an updated, reviewed, declustered, extensive, and homogeneous earthquake catalog (including detailed information about each event such as date and time, hypocentral location, and size), a triclustering algorithm has been applied to generate the seismogenic zones. The method seeks seismicity patterns in a quasi-objective manner following an initial assessment as to the best suited seismic parameters. The eight zones identified as part of this study are represented on maps to be analyzed, being the zone covered by the Arudy–Arette region to Bagneres de Bigorre as the one with the highest seismic hazard potential.

Earthquake precursors continue to be developed by researchers to try to predict earthquakes, one of which is Radon. The monitoring of radon gas in the ground continues to be carried out in Yogyakarta and its surroundings as one of the earthquake mitigation efforts. This study aims to analyze the variation of radon gas and seismic activity as well as the emergence of local earthquake precursors that occurred in Yogyakarta and its surroundings. Radon gas monitoring is carried out in two locations, namely in the Pundong and Piyungan areas. Earthquake activity was recorded from the BMKG earthquake catalog. The radon anomaly study to determine the existence of earthquake precursors was carried out using the correlation method. Radon gas anomalies are determined when there is an increase in the Radon concentration graph. The results show that an increase in radon gas emissions is correlated with an increase in earthquakes’ frequency. The correlation method’s application indicates the presence of radon gas anomalies as a precursor to earthquakes around the Opak Fault. Further research is needed to see the correlation and consistency of radon gas anomalies with earthquake events around the Opak Fault.

Triggered quakes get unconventional The big earthquakes induced by human activity are mostly linked with disposal of wastewater. However, Bao and Eaton implicate hydraulic fracturing (or fracking) as the culprit in western Canada (see the Perspective by Elsworth). Fracking near Fox Creek, Alberta, reactivated faults, clustering earthquakes along the old fault traces. Fracking does not appear to cause large earthquakes in many other areas that are prone to induced seismicity. Understanding the underlying causes of seismicity in different localities is vital for developing sound regulation to limit damaging earthquakes. Science , this issue p. 1406 ; see also p. 1380

In a study by Zare et al. (2014), a new earthquake catalog of the Middle East region has been developed consisting of historical, early, and modern instrumental events recorded between 1250 B.C. and 2006. This valuable effort was undertaken under the framework of the global earthquake model (GEM) and the earthquake model of the Middle East (EMME) projects. The final goal was to establish a unified catalog of seismicity by incorporating regional and international data to be used for homogeneous estimate of seismic hazards in the region (Erdik et al. 2012). However, observations show that magnitude of completeness (Mc) is not temporally and spatially homogeneous throughout the catalog. My goal in this commentary is to provide more insights on this important characteristic of the catalog and some suggestions on selection of homogeneous parts of the catalog. This can further aid users in using the catalog for different purposes.

A temporary seismic network consisting of 295 land stations was deployed in 2009 in Taiwan to monitor airgun sources during an onshore-offshore experiment in Taiwan. We exploit the continuously recorded dataset to detect and map seismicity in the seismically very active Taiwan. By combining recent automatic detection and phase picking techniques, we successfully generate an initial earthquake catalog of over 8400 events. The hypoDD algorithm is used to relocate and filter these events. This network recorded smaller events than the permanent regional network because of the many stations around the high mountain ranges and the generally high station density along 6 lines. The results based on the 2009 data generally reproduce the dominant seismicity features from many years of earthquake monitoring in Taiwan. In addition, we map hitherto unknown dipping zones under the Foothills and the Central Range that may correspond to seismogenic structures.

Source parameters of local earthquakes that occurred between 1998 and 2012 within the Kyrgyz seismological network (KNET) are used to study the patterns of stress drop in the Northern Tien Shan. The dynamic parameters of source radius r, the seismic moment M0, and the stress drop Ao are estimated for eighty seven M = 3.0-5.5 (K = 9.5-13.7) events, which make up 86% of earthquakes with this magnitude (99) for the period of observations. Earthquake mechanisms are determined either from P-wave arrivals (66 events) or by inversion (14 events). The distribution of earthquake mechanisms with the maximum (14 events) and minimum (14 events) stress drop shows that the amount of released stress correlates with slip geometry and revere-slip events contribute the most to the stress drop in the area. The spatial distribution of events with Ao > 0.9 MPa is compared with maps of kinematic parameters (Lode-Nadai coefficient or stress ratio, qo, and strain angle, o, based on average strain tensors according to the complete earthquake catalog for the Northern Tien Shan (1056 events for 1998-2012). The two sets of source parameters (r, M0, Ao and jio, o) correlate within the eastern Kyrgyz Range and the Karamoinok and Syndyk Ranges. © 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Local magnitude ( M L), body‐wave magnitude ( m b), and surface‐wave magnitude ( M s), which are saturated at certain values and may lead to an incorrect energy estimation of a large earthquake, are largely used in quantifying the size of an earthquake in western China. Based on the catalog from the China Earthquake Data Center (CEDC) and moment magnitude ( M w) provided by the Global Centroid Moment Tensor (Global CMT) Project, we test the general orthogonal regression (GOR) and the ordinary least‐squares (OLS) methods in M w– M L, M s, and m b conversions for earthquakes in three different tectonic structures of western China. For M L and m b, linear trends vary according to tectonic structures, which implies different body‐wave attenuations in the three structures. For M s, the results are similar, whether using the GOR or the OLS method, but slopes of regression lines are not close to 1, which indicates routine misestimates of M s in western China. The GOR slopes are uniformly larger than the OLS slopes in all magnitude conversions. Standard deviations are between 0.06 and 0.13 for the GOR method but are between 0.12 and 0.25 for the OLS. Thus, the GOR is found to be superior to the OLS method and its use is recommended. Conversions of different magnitudes to M w not only imply different patterns of seismic‐wave attenuations but will also benefit immediate assessment of seismic damage after occurrence of a destructive earthquake in the future. Online Material: Earthquake catalog and tables showing differences between magnitude estimates for M w, M L, m b, and M s.

Estimating the moment magnitudes ( M w ) of a small earthquake is a challenging task. One viable option to measure its size is to calculate its local magnitude ( M L ) and convert it to the physically based M w . Unfortunately, to correctly perform such a conversion is not easy; moreover, even though many studies demonstrate that the equivalence between M L and M w is incorrect for small events, these two parameters are sometimes thought to be strictly equivalent, regardless of the earthquake’s size. Using random vibration theory, we show that, below M w ∼4, the M L of a small earthquake is proportional to the logarithm of its seismic moment, and the following relationship holds: We test our findings on a high‐quality data set in the Upper Tiber Valley (northern Apennines, Italy), composed of events in the range of 0≤ M L ≤3.8, for which we compute accurate estimates of M L and M w . Online Material: Details of the processing procedure, figures of the empirical regional attenuation functional, and source terms of 1191 events from the Alto Tiberina fault (ATF) data set and earthquake catalog.

A significant seismic quiescence in Taiwan was reported by Wu and Chiao (2006) before the occurrence of the 1999 M w 7.6 Chi‐Chi earthquake. A similar kind of activity was also observed in the 2012 earthquake catalog reported by Central Weather Bureau (CWB). Seven months in the 2012 catalog seem to have lower monthly seismicity rates than the one standard deviation below the mean (673±82) for earthquakes with M L ≥2.0. Here, we checked the seismic network in Taiwan and found that some new seismic stations, including the Broadband Array in Taiwan for Seismology (BATS), were incorporated within the Taiwan Central Weather Bureau Seismic Network (CWBSN) since 2012. Most of these BATS stations are located on hard‐rock sites, which may affect magnitude estimation because of their site characteristics. To account for the impact of site effect, earthquake catalog data during the period of 1994 to 2014 was collected and station correction was calculated for each station. A strong correlation is found between station corrections determined in this study and geological settings of the region. Stations located on soil sites have high amplifications with negative station corrections. On the other hand, stations located on hard‐rock sites have low amplifications with positive station corrections. After applying station correction, the mean seismicity rate is found to be 716 events per month with a standard deviation of 76 events for earthquakes with M L ≥2.0. We conclude that the reason behind the apparent low seismicity in 2012 is due to the installation of new seismic stations on rock sites, which lead to underestimation of M L .

Seismic hazards in the Ordos Block and its periphery were estimated based on 500 years of intensity observations. Firstly, historical intensity observations were collected, the completeness of the earthquake catalog was tested, and aftershocks were deleted. Secondly, the intensity data were digitized and placed in a geographic information system (GIS). Finally, the digitized intensity data were analyzed to determine the frequency–intensity relationship (i.e., seismic hazard curve) for each cell. The seismic hazards were quantified by the intensity and return period in a site or an area. Assuming a Poisson distribution for the earthquake occurrence in time, a probability of I ≥VII, VIII, or IX in 50 years was quantified. We also estimated the corresponding intensities with 10% probability of exceedance in 50 years. The results show that the periphery of Ordos Block faces significant seismic hazards. Our study also suggests that the current designed peak ground acceleration or intensity for Ordos Block may not be adequate.

The parameters of earthquakes in northeast of Russia that occurred in 1735–1910 and were published in New Catalog of Earthquakes in USSR from Ancient Times trough 1975 have been specified based on the initial data presented (1977). Special attention has been paid to the conformity between the initial data, the available solution methods, and the resulting parameter values. The macroseismic data from the preinstrumental and instrumental observational periods have been compared.