Instrumental Catalog Research Articles

Qualifying for international and national protection under the Polish legal order: Some remarks in the context of the war in Ukraine

The Russian Federation's actions against Ukraine in February 2014, having - at the time - the form of hybrid warfare, followed later by an armed assault that took place on 24 February 2022, have resulted in an unprecedented influx of refugees from across Poland's eastern border. As Poland faced a major challenge (also in legal terms), additional regulations had to be introduced to supplement the refugee protection standards already in place under national and international laws. The purpose of this paper is to identify the prerequisites (conditions) stemming from the catalogue of protective instruments provided for in Polish legal regulations that can be taken advantage of by Ukrainian citizens after the Russian attack of 24 February 2022. The thesis of this study is that Polish protective mechanisms are consistent and complementary, and that, insofar as they apply to Ukrainian citizens, they fulfil international obligations under the Convention relating to the Status of Refugees, adopted on 28 July 1951 and secondary European Union law, mainly Directive 2011/95/EU of the European Parliament and of the Council of 13 December 2011.

B‐More‐Incomplete and b‐More‐Positive: Insights on a Robust Estimator of Magnitude Distribution

AbstractThe b‐value in earthquake magnitude‐frequency distribution quantifies the relative frequency of large versus small earthquakes. Monitoring its evolution could provide fundamental insights into temporal variations of stress on different fault patches. However, genuine b‐value changes are often difficult to distinguish from artificial ones induced by temporal variations of the detection threshold. A highly innovative and effective solution to this issue has recently been proposed by van der Elst (2021, https://doi.org/10.1029/2020jb021027) by means of the b‐positive estimator, which is based on analyzing only the positive differences in magnitude between successive earthquakes. Here, we demonstrate the robustness of the estimator, which remains largely unaffected by detection issues due to the properties of conditional probability. We illustrate that this robustness can be further improved by considering positive differences in magnitude, not only between successive earthquakes but also between different pairs of earthquakes. This generalized approach, defined as the “b‐more‐positive estimator,” enhances efficiency by providing a precise estimate of the b‐value while including a larger number of earthquakes from an incomplete catalog. However, our analysis reveals that the accuracy of the b estimators diminishes when earthquakes below the completeness threshold are included in the catalog. This leads to the paradoxical observation that greater efficiency is achieved when the catalog is more incomplete. To address this, we introduce the “b‐more‐incomplete estimator,” where the b‐more‐positive estimator is applied only after artificially filtering the instrumental catalog to make it more incomplete. Our findings show the superior efficiency of the b‐more‐incomplete method.

Seismic events in the Sverdlovsk region for the period 1788–2022

Introduction. Sverdlovsk region is a major industrial center. There are mining enterprises, chemical plants, reservoirs, and high-capacity power plants. These objects are located close to large settlements. Currently, about 400 seismic events are recorded annually in the region. To ensure the seismic safety of objects of increased responsibility and especially important construction objects, it is necessary to carry out studies on detailed seismic zoning of the territory under consideration. The results of this work are the first stage of these studies. Research theory. For the first time, a consolidated unified catalog of seismic events that occurred on the territory of the Sverdlovsk region was compiled. Historical and instrumental catalog data for the period 1788–2022 and data from instrumental records of local seismic events recorded by temporary, mobile stations of the Institute of Geophysics Ural Branch of the Russian Academy of Sciences (IGF UB RAS) served as the basis. served as the basis. Results. Most of the recorded events are technogenic. Mostly these are industrial explosions and rock burst. These seismic events are recorded in the area of the following cities: Asbest, Ekaterinburg, Revda, Nizhny Tagil, Kushva, Kachkanar, Karpinsk, Severouralsk. Tectonic earthquakes have also been repeatedly recorded in the Sverdlovsk region. Most of them are not felt by people. Earthquakes with a magnitude greater than 4.0 have macroseismic manifestations. The strongest earthquake is 08.17.1914 (MS= 5.0, epicenter coordinates 57.09° N, 59.8° E). The intensity of the earthquake at the epicenter was 6.0 on the MSK-64 scale. The results of this work will serve as a basis for further determination of the parameters of the seismic regime of the study area.

Spatio-temporal variations of seismic coupling along a transform fault: the western North Anatolian Fault Zone

SUMMARY The Main Marmara Fault (MMF) forms a major segment of the North Anatolian Fault Zone (NAFZ) in northwestern Türkiye. The MMF represents a seismic gap with currently high seismic hazard and associated risk for the Istanbul metropolitan area. Here we estimate the seismic coupling defined as the ratio of the seismic strain rate to the tectonic strain rate, for the MMF and adjacent NAFZ segments. This ratio indicates the fraction of total strain accumulated with time that is released seismically. We compare the results of seismic strain rates and coupling estimated from earthquakes included in historical and instrumental catalogues, which allows us to identify fault segments that represent a considerable seismic threat during the current seismic cycle. We find that along the main fault traces hosting the large events, seismic strain rates from the historical catalogue are of the same order as the tectonic strain rates. In contrast, coupling estimates based on seismic data from the instrumental catalogue covering also off-fault areas, are up to 100 times smaller, highlighting that most of the seismic energy is released in large earthquakes with recurrence times longer than the time covered by the instrumental catalogue. Within the Sea of Marmara, a significant portion (48%) of shear strain from the instrumental catalogue is currently being accommodated by seismic deformation. Significant variations of the seismic coupling are observed before and after the 1999 M > 7 Izmit earthquake, highlighting the different contribution of aseismic slip over different portions of the seismic cycle. A comparison of the temporal evolution of the 1999 Izmit and Düzce post-seismic deformation with seismic strain rates shows that the largest seismic strain rates coincide with the largest post-seismic deformation.

Compilation of Regional Homogeneous Seismic Catalog for Identification of Tsunamigenic Zones in the Black Sea Region

Although tsunamis in the Black Sea are rare and less destructive, recently, their study has been the subject of interest due to the increasing concentration of population and infrastructure in low-lying coastal areas. This study aims to elucidate the spatial–temporal characteristics of earthquakes in the Black Sea region (27° E–42° E and 40° N–47° N) over a century to clarify the seismicity pattern further to be used for probabilistic seismic and tsunami hazard analysis. Significant volumes of seismic data from international and national databases were analyzed, and the results obtained from previous research were supplemented and expanded. Earthquakes over the period 1905–2022 from eight up-to-date seismic catalogs were used to compile a unified catalog after conversion to the moment magnitude scale Mw. The best-fit linear relationship between several magnitude scales and Mw was determined using the general orthogonal regression (GOR) and the least squares method (LSM). After the declustering procedure, the compiled catalog consists of 18,528 unique events. To assess the catalog data quality, the magnitude of completeness Mc was estimated for the entire catalog (1905–2022) and the so-called instrumental catalog (1977–2022). In addition, the spatial distribution of the completeness magnitude Mc and the recurrence b-plot slope in the Gutenberg–Richter distribution law were assessed using the goodness-of-fit and maximum likelihood methods from the instrumental catalog data. Finally, the most significant earthquakes within the Black Sea boundaries were estimated with their parameters and focal mechanisms. A possibility of the realization of strong quakes in the near future with tsunamigenic potential in the Black Sea region was concluded.

How many strong earthquakes will there be tomorrow?

In this note, we study the distribution of earthquake numbers in both worldwide and regional catalogs: in the Global Centroid Moment Tensor catalog, from 1980 to 2019 for magnitudes Mw 5. 5+ and 6.5+ in the first case, and in the Italian instrumental catalog from 1960 to 2021 for magnitudes Mw 4.0+ and 5.5+ in the second case. A subset of the global catalog is also used to study the Japanese region. We will focus our attention on short-term time windows of 1, 7, and 30 days, which have been poorly explored in previous studies. We model the earthquake numbers using two discrete probability distributions, i.e., Poisson and Negative Binomial. Using the classical chi-squared statistical test, we found that the Poisson distribution, widely used in seismological studies, is always rejected when tested against observations, while the Negative Binomial distribution cannot be disproved for magnitudes Mw 6.5+ in all time windows of the global catalog. However, if we consider the Japanese or the Italian regions, it cannot be proven that the Negative Binomial distribution performs better than the Poisson distribution using the chi-squared test. When instead we compared the performances of the two distributions using the Akaike Information Criterion, we found that the Negative Binomial distribution always performs better than the Poisson one. The results of this study suggest that the Negative Binomial distribution, largely ignored in seismological studies, should replace the Poisson distribution in modeling the number of earthquakes.

A fault-based probabilistic seismic hazard model for Lebanon, controlling parameters and hazard levels

The present work develops a comprehensive probabilistic seismic hazard study for Lebanon, a country prone to a high seismic hazard since it is located along the Levant fault system. The historical seismicity has documented devastating earthquakes which have struck this area. Contrarily, the instrumental period is typical of a low-to-moderate seismicity region. The source model built is made of a smoothed seismicity earthquake forecast based on the Lebanese instrumental catalog, combined with a fault model including major and best-characterized faults in the area. Earthquake frequencies on faults are inferred from geological as well as geodetic slip rates. Uncertainties at every step are tracked and a sensitivity study is led to identify which parameters and decisions most influence hazard estimates. The results demonstrate that the choice of the recurrence model, exponential or characteristic, impacts the most the hazard, followed by the uncertainty on the slip rate, on the maximum magnitude that may break faults, and on the minimum magnitude applied to faults. At return periods larger than or equal to 475 years, the hazard in Lebanon is fully controlled by the sources on faults, and the off-fault model has a negligible contribution. We establish a source model logic tree populated with the key parameters, and combine this logic tree with three ground-motion models (GMMs) potentially adapted to the Levant region. A specific study is led in Beirut, located on the hanging-wall of the Mount Lebanon fault to understand where the contributions come from in terms of magnitudes, distances and sources. Running hazard calculations based on the logic tree, distributions of hazard estimates are obtained for selected sites, as well as seismic hazard maps at the scale of the country. Considering the PGA at 475 years of return period, mean hazard values found are larger than 0.3 g for sites within a distance of 20–30 km from the main strand of the Levant Fault, as well as in the coastal region in-between Saida and Tripoli (≥ 0.4 g considering the 84th percentile). The study provides detailed information on the hazard levels to expect in Lebanon, with the associated uncertainties, constituting a solid basis that may help taking decisions in the perspective of future updates of the Lebanese building code.

Fault-based probabilistic seismic hazard analysis in regions with low strain rates and a thick seismogenic layer: a case study from Malawi

SUMMARY Historical and instrumental earthquake catalogs in low strain rate regions are not necessarily indicative of the long-term spatio-temporal distribution of seismicity. This implies that probabilistic seismic hazard analysis (PSHA) should also consider geologic and geodetic data through fault-based seismogenic sources. However, it is not always clear how on-fault magnitude-frequency distributions (MFDs) should be described and, if the seismogenic layer is especially thick, how fault sources should be extrapolated down-dip. We explore these issues in the context of a new PSHA for Malawi, where regional extensional rates are 0.5–2 mm yr−1, the seismogenic layer is 30–40-km thick, the instrumental catalog is ∼60 yr long and fault-based sources were recently collated in the Malawi Seismogenic Source Model. Furthermore, Malawi is one of several countries along the East African Rift where exposure to seismic hazard is growing, but PSHA does not typically consider fault sources. We use stochastic event catalogs to explore different fault source down-dip extents and MFDs. Our PSHA indicates that hazard levels are highest for a Gutenberg–Richter on-fault MFD, even at low probabilities of exceedance (2 per cent in 50 yr), whilst seismic hazard levels are also sensitive to how relatively short (<50 km) fault sources are extrapolated down-dip. For sites close to fault sources (<40 km), seismic hazard levels are doubled compared to previous instrumental-seismicity based PSHA in Malawi. Cumulatively, these results highlight the need for careful fault source modelling in PSHA of low strain rate regions and the need for new fault-based PSHA elsewhere in the East Africa Rift.

Data analysis of the unsteadily accelerating GPS and seismic records at Campi Flegrei caldera from 2000 to 2020

Ongoing resurgence affects Campi Flegrei caldera (Italy) via bradyseism, i.e. a series of ground deformation episodes accompanied by increases in shallow seismicity. In this study, we perform a mathematical analysis of the GPS and seismic data in the instrumental catalogs from 2000 to 2020, and a comparison of them to the preceding data from 1983 to 1999. We clearly identify and characterize two overlying trends, i.e. a decennial-like acceleration and cyclic oscillations with various periods. In particular, we show that all the signals have been accelerating since 2005, and 90–97% of their increase has occurred since 2011, 40–80% since 2018. Nevertheless, the seismic and ground deformation signals evolved differently—the seismic count increased faster than the GPS data since 2011, and even more so since 2015, growing faster than an exponential function The ground deformation has a linearized rate slope, i.e. acceleration, of 0.6 cm/yr2 and 0.3 cm/yr2 from 2000 to 2020, respectively for the vertical (RITE GPS) and the horizontal (ACAE GPS) components. In addition, all annual rates show alternating speed-ups and slow-downs, consistent between the signals. We find seven major rate maxima since 2000, one every 2.8–3.5 years, with secondary maxima at fractions of the intervals. A cycle with longer period of 6.5–9 years is also identified. Finally, we apply the probabilistic failure forecast method, a nonlinear regression that calculates the theoretical time limit of the signals going to infinity (interpreted here as a critical state potentially reached by the volcano), conditional on the continuation of the observed nonlinear accelerations. Since 2000, we perform a retrospective analysis of the temporal evolution of these forecasts which highlight the periods of more intense acceleration. The failure forecast method applied on the seismic count from 2001 to 2020 produces upper time limits of [0, 3, 11] years (corresponding to the 5th, 50th and 95th percentiles, respectively), significantly shorter than those based on the GPS data, e.g. [0, 6, 21] years. Such estimates, only valid under the model assumption of continuation of the ongoing decennial-like acceleration, warn to keep the guard up on the future evolution of Campi Flegrei caldera.

Perception of neonatology staff regarding the availability of equipment and supplies for the care of patients in need of nCPAP.

Respiratory distress syndrome (RDS) is Mexico's second leading cause of neonatal mortality. The 75% reduction in mortality due to RDS has been attributed to the use of nasal continuous positive airway pressure (nCPAP). A survey was conducted to determine the perception of the medical staff regarding the availability of nCPAP equipment and supplies in Mexican hospitals with neonatal intensive care units (NICUs). We sent a survey via e-mail to several neonatologists in each state of the country, requesting only one response per hospital. We performed statistical analysis with SPSS software. We received 195 surveys from private (HPri) and public (HPub) hospitals with NICUs nationwide: 100% of HPri and 39% of HPub. More than 75% of the nursing and medical staff had received formal training in nCPAP in 11% of HPri and 5% of HPub. The perceived availability of CPAP equipment was 83.7% vs. 52.1%; nasal cannula supply, 75.5% vs. 36.3%; air/oxygen blender availability, 51.0% vs. 32.9%, in HPri and HPub, respectively. The observed differences were statistically significant. Significant differences were also found among healthcare institutions. The availability of CPAP equipment and consumables between HPub and HPri is unbalanced and is lower in public institutions. Bubble CPAP is not included essential equipment in the national catalog of instruments and equipment for public hospitals, and its request is complicated. The training of CPAP staff and the availability of bubble CPAP and supplies in public hospitals should be improved.

Rupture styles linked to recurrence patterns in seismic cycles with a compliant fault zone

Seismic cycles emerge in a broad range of rupture styles, from slow-slip events to pulse-like earthquake sequences. Meanwhile, large earthquakes in paleoseismic and instrumental catalogues exhibit various recurrence patterns going from periodic to chaotic cycles with characteristic or dissimilar ruptures. The potential connection between these observations is still poorly known. Here, we investigate the link between rupture styles and recurrence patterns in quasi-dynamic models of seismicity in two-dimensional faults embedded in a compliant zone, exploring a wide range of frictional and fault zone properties. The recurrence patterns evolve from purely periodic to multiple-periodic time- and slip-predictable cycles, to chaotic sequences of super-cycles with full and partial ruptures with an increasing number of aftershocks. This transition is accompanied by changes of rupture styles from crack-like to pulse-like ruptures. These behaviors can be obtained either by a more compliant fault zone or a reduced characteristic weakening distance of friction. The effects of the compliant zone and other physical characteristics can be conflated into a single non-dimensional number, such that seismic cycles with similar behaviors can be obtained with or without a compliant fault zone in quasi-dynamic simulations. The connection between recurrence patterns and rupture styles implies that the paleoseismic record can bring useful constraints to rupture characteristics and fault zone properties.

Tectonic geomorphology of active faults in Eastern Crete (Greece) with slip rates and earthquake history from cosmogenic 36Cl dating of the Lastros and Orno faults

In eastern Crete, several normal faults trend both NNE-SSW and E-W. Most of them form impressive bedrock fault scarps indicating ongoing extension in the Hellenic fore-arc. No earthquakes from historical and instrumental catalogues can be directly associated with these faults. Geomorphologic profiles across five different faults in sites well-preserved from erosion, deposition or human intervention revealed displacements of ∼6.9 m–∼30 m. Following a robust site selection at the Lastros and Orno faults, we mapped different categories of weathered horizontal ribbons along the bedrock fault plane based on colour contrast, lichen colonisation and karstic features that affect fault plane roughness, features that altogether are interpreted as earthquake horizons. The data indicate coseismic displacements of 15–35 cm for the last three earthquakes at the Lastros fault and 10–20 cm for the last two earthquakes at the Orno fault. To constrain the age of these earthquakes and to estimate millennial fault slip rates, we determined cosmogenic 36Cl concentrations from vertical profiles composed of 24 samples from the exposed Lastros fault plane and 7 samples of the Orno fault plane. Bayesian Markov Chain Monte Carlo (MCMC) modelling implies that the last three earthquakes at the Lastros fault, occurred within the last 1.8 ± 1.2 kyr (EQ1 = 1.1 ± 1.1 kyr, EQ2 = 1.4 ± 1.1 kyr, EQ3 = 1.8 ± 1.2 kyr). Furthermore, Lastros’ slip rate varied with a rate of 0.6 ± 0.3 mm/yr during the last 1.8 ± 1.2 kyr, preceded by a rate of 1.1 ± 0.4 mm/yr from ∼1.8 to 8 kyr; suggesting periods of earthquake clustering. At the Orno fault, the last two earthquakes occurred within the last ∼3.5 kyr accompanied with a slip rate of 0.16+0.06-0.02 mm/yr during postglacial times. This confirms for the first time based on absolute dating, that both NNE-SSW and E-W trending neighbouring faults in Crete were active during the Holocene.Most of the 13.2 m high Orno fault scarp was exhumed during glacial times, with an apparent slip rate of 0.28+0.12-0.07 mm/yr. The upper part of the Lastros fault scarp (9–12 m) and the apparent age of the four Lastros footwall samples (∼17.9 kyr, ∼26.0 kyr, ∼29.9 kyr, ∼37.4 kyr) underline the long preservation throughout glacial times as well. These findings show that the general hypothesis of predominantly postglacial bedrock fault scarps needs to be regarded with caution at lower latitudes and/or low altitudes (<1000 m), since degradation processes are weaker.

Comparative Analysis of the Methods for Estimating the Magnitude of Completeness of Earthquake Catalogs

—The magnitude of completeness {{M}_{c}} of the earthquakes above which 100% of events are thought to be reliably detected is a vital parameter characterizing the completeness of seismic data. A known fact is that to obtain correct estimates of the parameters of seismicity, it is compulsory to take into account {{M}_{c}} variations in space and time. In this work, we compare six modern methods for estimating {{M}_{c}}. To compare the methods, we use event samples from real instrumental earthquake catalogs and synthetic catalogs generated based on the three models of magnitude distribution. We analyze the dependences of the two first moments of the distributions of {{M}_{c}} estimates on the shape of magnitude distributions and the sample size. We use three models corresponding to sample distributions that occur in the analysis of instrumental earthquake catalogs. Based on the obtained results, we formulate recommendations on selecting the suitable method for estimating the magnitude of completeness {{M}_{c}}.

An Earthquake Simulator for New Zealand

ABSTRACTWe present an earthquake simulator for New Zealand. It uses the Rate-and-State Earthquake Simulator engine based on approximations of the rate-and-state friction equations. The full set of faults considered in the most recent New Zealand national seismic hazard maps are included in the simulator. New simulator methods are introduced that allow for the inclusion and interaction between upper plate faults and a subduction interface fault below them. The simulator generates sequences of complex slip events and a catalog of finite ruptures hundreds of thousands of years in length. Results from the simulator are evaluated through statistical testing and comparison with geological and geophysical observations. These evaluations include a spatial comparison against historical earthquakes, a comparison against rates of events in the instrumental catalog, and a comparison against scaling relations. Consistency of the model with these measures is generally found, though some differences with productivity is noted, due to incomplete modeling of subducting slab features like geodetically inferred spatially dependent creep and dense faulting in Bay of Plenty faults. Significant emergent aspects of the resulting synthetic catalog are discussed. These include substantial variability over instrumental catalog timescales, clustering of large events in space and time, and spontaneous ruptures that break both the upper crustal faults and subduction interface coseismically. An online repository provides the model output, and an additional site provides python code for reproducing some of the figures in this article and tools for further model output analysis.

Automatic picking and probabilistic location for earthquake assessment in the Lesser Antilles subduction zone (1972–2012)

Instrumental catalogues of earthquakes in the subduction zone of the Lesser Antilles are produced by local observatories and the International Seismological Centre. But none of these catalogues merge all arrival times of the first regional phases available; in addition, they have a magnitude of completeness relatively high for the entire Lesser Antilles area. As part of the Antilles Seismological Data Centre project, we produced a unified catalogue of known earthquakes from 1972 to 2012, with optimal constraints on the hypocentre locations. We re-evaluated the hypocentres with the method used in local observatories and a probabilistic method improving the distributions of arrival time residuals. We developed a simple method to select the preferred hypocentre independently of the localization algorithm, and we offer a complete catalogue including 46,703 earthquakes. Compared to other existing catalogues, we provide additional arrival times for 24,528 earthquakes. Our results highlight the variabilities of the magnitude of completeness and of the seismicity suggesting how the future analysis could infer the mechanisms of heterogeneous seismic coupling and intermediate-depth triggering.

Zaskarżalność uchwał Państwowej Komisji Wyborczej w trybie art. 161a Kodeksu wyborczego

The aim of this study is to analyse the operation of a new institution in the form of a complaint by the electoral representative against the resolutions of the National Electoral Commission in the form of guidelines and explanations, as well as to assess the legitimacy of the implementation of this institution into the Polish electoral law. On the one hand, there is no doubt that this solution contributes to the implementation of a long-reported postulate for the decisions of the election administration to be brought under judicial control, and also influences the extension of the catalogue of instruments for social control of the election process. On the other hand, however, it is impossible to analyse a venture of this institution with complete disregard for other conditions of the election process. The analysis is intended to provide an answer to the question of whether the complaint against the resolutions of the National Electoral Commission, as referred to in Article 162a of the Polish Election Code, in its current form is a desirable component of the Polish electoral law, or is it rather an institution limiting the efficiency of the election process. In the study, the construction of Article 161a of the Election Code was examined using a formal and legal method, and the consequences of the application of the new solution in election practice were analysed using an empirical method and the achievements of the doctrine of constitutional law.

Statistical analysis of earthquake catalogs for seismic hazard studies around the Karliova Triple Junction (eastern Turkey)

A complete and comprehensive earthquake catalog is a substantial input to do probabilistic seismic hazard analysis. The Karliova triple junction (eastern Turkey) is characterized by an active seismicity mostly in the shallow crust. Origin times, earthquake locations, and magnitudes reported by the Kandilli Observatory and Earthquake Research Institute, Boğaziçi University (KOERI) and three international agencies (ISC, IRIS and EMSC) in the region bounded by latitudes 37.5° and 40.5° N and longitudes 37.5° and 42.5° E have been gathered in order to quantify the seismicity around the study area and calculate associated seismic parameters. The Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters (a- and b-values) have been estimated. The same Mc value of 2.7 has been obtained for all catalogs. After 2014, all earthquakes with magnitudes higher than 2.0 are reliably recorded. However, the b-value varied from 0.97 to 1.28. High b-value anomalies mostly for earthquakes with shallow depths (5–15 km) have been observed. A relatively lower b-values are found at depths <5 km. The most probable largest annual earthquakes are around Mw = 5.8. The seismic hazard parameters i.e. the maximum regional magnitude mmax, mean seismic activity rate λ, the slope of the frequency–magnitude Gutenberg–Richter relationship, and the β value (bln(10)) have been estimated. Using the Bayesian model for the earthquake occurrence in time and earthquake magnitude, which incorporates seismic information from historical and instrumental catalogs, the hazard parameters are presented in terms of the probability of exceedance for 1- 10- 50- and 100-year return periods with a b-value equal to 1.19 and mmax equal to 8.05. The highest probability of earthquakes, which may occur in an interval of 50 years is estimated as Mw = 7.0. The average recurrence interval of earthquakes with magnitudes 6.7 and 7.8 (the maximum observed magnitudes at KOERI catalog and instrumental earthquakes in the region, respectively) are ∼27 and ∼488 years.

Perspectives on Clustering and Declustering of Earthquakes

Abstract Clustering is a fundamental feature of earthquakes that impacts basic and applied analyses of seismicity. Events included in the existing short-duration instrumental catalogs are concentrated strongly within a very small fraction of the space–time volume, which is highly amplified by activity associated with the largest recorded events. The earthquakes that are included in instrumental catalogs are unlikely to be fully representative of the long-term behavior of regional seismicity. We illustrate this and other aspects of space–time earthquake clustering, and propose a quantitative clustering measure based on the receiver operating characteristic diagram. The proposed approach allows eliminating effects of marginal space and time inhomogeneities related to the geometry of the fault network and regionwide changes in earthquake rates, and quantifying coupled space–time variations that include aftershocks, swarms, and other forms of clusters. The proposed measure is used to quantify and compare earthquake clustering in southern California, western United States, central and eastern United States, Alaska, Japan, and epidemic-type aftershock sequence model results. All examined cases show a high degree of coupled space–time clustering, with the marginal space clustering dominating the marginal time clustering. Declustering earthquake catalogs can help clarify long-term aspects of regional seismicity and increase the signal-to-noise ratio of effects that are subtler than the strong clustering signatures. We illustrate how the high coupled space–time clustering can be decreased or removed using a data-adaptive parsimonious nearest-neighbor declustering approach, and emphasize basic unresolved issues on the proper outcome and quality metrics of declustering. At present, declustering remains an exploratory tool, rather than a rigorous optimization problem, and selecting an appropriate declustering method should depend on the data and problem at hand.

The Measurement of Food Insecurity in High-Income Countries: A Scoping Review.

The measurement of food insecurity is essential to monitor the prevalence, risk factors, consequences and effects of food insecurity and the interventions and policies implemented to tackle it. Yet, how best to apply it remains an unsettled issue due to the multifaceted and context-dependent nature of food insecurity. We report a scoping review of measures of food insecurity at the individual and household level in high-income countries with the final purpose of facilitating a catalogue of instruments to be used by both researchers and practitioners. The scoping review was conducted following the methodological framework of Arksey and O’Malley and the Joanna Briggs Institute guidelines. We included all types of documents published between 2000–2020 using instruments that estimate food insecurity at both individual and household level in high-income countries, and with respondents including adolescents, adults, and elderly. We identified a total of 23 measurement strategies being used in 33 peer-reviewed publications and 114 documents from the grey literature. Our results show that most measures focus on the access dimension of food insecurity and that further research is required to develop measures that incorporate aspects of quality of dietary intake and relevant individual, household and social conditions related to food insecurity.

A pragmatic approach to adjusting early instrumental local magnitudes for seismic hazard assessments in Australia

Prior to the development of Australian-specific magnitude formulae, the 1935 magnitude correction factors by Charles Richter—originally developed for southern California—were almost exclusively used to calculate earthquake magnitudes throughout Australia prior to the 1990s. Due to the difference in ground-motion attenuation between southern California and much of the Australian continent, many earthquake magnitudes from the early instrumental era are likely to have been overestimated in the Australian earthquake catalogue. A method is developed that adjusts local magnitudes (ML) using the difference between the original (inappropriate) magnitude formulae (or look-up tables) and the Australian-specific formulae at a distance determined by the nearest recording station likely to have recorded the earthquake. Nationally, these adjustments have reduced the number of earthquakes of ML ≥ 4.5 in the early instrumental catalogue by approximately 25% since 1900, while the number of ML ≥ 5.0 earthquakes has reduced by approximately 32% over the same time period. The reduction in the number of moderate-to-large-magnitude earthquakes over the instrumental period yields long-term earthquake rates that are more consistent with present-day rates, since the development of Australian-specific magnitude formulae (approximately 1990). The adjustment of early instrumental magnitudes to obtain consistently derived earthquake catalogue is important for seismic hazard assessments.