Earthquake Catalog Research Articles

A neural encoder for earthquake rate forecasting

Forecasting the timing of earthquakes is a long-standing challenge. Moreover, it is still debated how to formulate this problem in a useful manner, or to compare the predictive power of different models. Here, we develop a versatile neural encoder of earthquake catalogs, and apply it to the fundamental problem of earthquake rate prediction, in the spatio-temporal point process framework. The epidemic type aftershock sequence model (ETAS) effectively learns a small number of parameters to constrain the assumed functional forms for the space and time correlations of earthquake sequences (e.g., Omori-Utsu law). Here we introduce learned spatial and temporal embeddings for point process earthquake forecasting models that capture complex correlation structures. We demonstrate the generality of this neural representation as compared with ETAS model using train-test data splits and how it enables the incorporation additional geophysical information. In rate prediction tasks, the generalized model shows >4% improvement in information gain per earthquake and the simultaneous learning of anisotropic spatial structures analogous to fault traces. The trained network can be also used to perform short-term prediction tasks, showing similar improvement while providing a 1000-fold reduction in run-time.

Effects on Probabilistic Seismic Hazard Estimates That Result from Nonuniqueness in Declustering an Earthquake Catalog

ABSTRACT Declustering a seismicity catalog to obtain a background seismicity model for probabilistic seismic hazard analysis is not a uniquely defined process. Zaliapin and Ben-Zion (2020) present a method for randomly thinning a complete catalog by removing nearest-neighbor earthquakes. The number of events in the residual catalog depends on a continuous parameter, α0, called the “cluster threshold.” Varying α0 results in a family of residual catalogs, and when enough events are removed the catalog is nearly Poissonian and can be considered declustered. This family of thinned catalogs is used to generate a corresponding family of background seismicity models, which in turn are used to find the probabilistic seismic hazard on an east–west profile across California. Additional models are developed by renormalizing the thinned Zaliapin and Ben-Zion (2020) catalogs to the catalog rate of earthquakes with moment magnitude Mw≥5 and from the maximum shaking earthquake catalog of Anderson et al. (2021). Adding fault contributions, the simplified estimate of the hazards with probability of exceedance of 2% in 50 yr are comparable to the 2018 National Seismic Hazard Model (NSHM). Where faults dominate the hazard, the method of thinning has little effect. The range of hazard estimates from the set of background models alone illustrate the range of effects of catalog thinning for any location where faults do not dominate. The spread of background hazard estimates at most sites is generally within a multiplicative factor of ∼2 of the hazard estimated from a catalog declustered for the 2018 NSHM. However, the spread in the estimates is very large in the vicinity of aftershock zones of large earthquakes. The family of randomly thinned catalogs, including alternative smoothing parameters and optional rescaling, may span the body and range of background hazard that can be inferred from the known history of earthquakes.

Study of Seismicity Based on the Results of Hypocenter Relocation Using Double Difference (HypoDD) Method in West Sumatera and Its Surrounding

The presence of the Indo-Australian plate, the Eurasian plate and the active Sumatra fault zone makes the West Sumatra region and its surroundings have very high seismic activity. To describe the seismicity pattern, it is necessary to analyze the earthquake hypocenter relocation, one of which is using the double difference (hypoDD) method. This method basically uses the data residual travel time from each hypocenter pair to the earthquake seismic station. The purpose of this research is to analyze the relocation of the hypocenter and describe the seismicity pattern in the West Sumatra and surrounding areas. The data used in this study are the time arrivals of P and S waves during the period of 2022 obtained from the earthquake catalog at the Padang Panjang Geophysical Station. The results showed that the earthquake hypocenter was relocated 888 out of 934 earthquake events and the distribution of hypocenter relocation produces a good seismicity pattern. From the results of the earthquake hypocenter relocation, the seismicity pattern in the West Sumatra region and its surroundings is generally influenced by subduction zones and some due to active fault zones. Seismicity in the subduction zone and active faults of Sumatra has a depth of about 50 - 250 km and 5 - 20 km. This indicates that during the period of 2022, subduction zones with medium to deep depths are very active as well as in Sumatra's active fault zones, especially in the Sianok segment.

Exploring Seismic Hazard in the Groningen Gas Field Using Adaptive Kernel Smoothing

The discovery of gas in Groningen in 1959 has been a massive boon to the Dutch economy. From the 1990s onwards, though, gas production has led to induced seismicity. In this paper, we carry out a comprehensive exploratory analysis of the spatio-temporal earthquake catalogue. We develop a non-parametric adaptive kernel smoothing technique to estimate the spatio-temporal hazard map and to interpolate monthly well-based gas production statistics. Second- and higher-order inhomogeneous summary statistics are used to show that the state-of-the-art rate-and-state models for the prediction of seismic hazard fail to capture inter-event interaction in the earthquake catalogue. Based on these findings, we suggest a modified rate-and-state model that also takes into account changes in gas production volumes and uncertainty in the pore pressure field.

Revisiting Vrancea (Romania) Intermediate-Depth Seismicity: Some Statistical Characteristics and Seismic Quiescence Testing

Background: The intermediate-depth seismicity in the Vrancea region (Romania) is characterized by localized and persistent earthquake activity that culminates about two or three times in a century with the occurrence of a large event (M ≥ 6.5). Here we have revisited some important seismicity characteristics, using earthquake catalog data spanning two different time periods: 1960–1999 and 2005–2013. Methods: we have determined the b-value of the frequency-magnitude distribution of earthquakes, using a maximum likelihood procedure, and estimated the parameter β to quantify anomalous seismicity rate decreases and increases. Results: by using data from the first period, we have confirmed the existence of a decreased b-value in the deepest part of the seismogenic zone; by using data from the second period, we have statistically confirmed the seismic quiescence that preceded the occurrence of the 1977 M7.4 Vrancea earthquake. Conclusions: the decreased b-value has been interpreted either in terms of an increased lithostatic stress with depth or as an indicator of the depth range where the next major Vrancea earthquake may occur. The time variation of the seismicity parameter β may reveal anomalous seismic quiescence and increased earthquake rates that may precede the occurrence of large earthquakes.

Improving seimic hazard assessment in the Mediterranean Region

This paper is intended as a short presentation of the main limitations affecting seismic hazard assessment, revisiting possible methods available in the literature to be applied for this purpose. The convergence of the African Plate with the Eurasian Plate is the cause of the high seismic activity characterizing the Mediterranean region, with particular intensity in its eastern part. It is clear that the associated seismic risk requires appropriate measures for its mitigation. Seismic risk, the amount of resources that the community is expected to pay to earthquakes in the long term, is the product of three factors, such as seismic hazard, vulnerability and value of the exposed goods. As earthquakes cannot be prevented, seismic risk can be mitigated by improving our knowledge of seismic hazard, which is largely based on statistical analysis of historical earthquake catalogs. Nevertheless, historical records are affected by problems of reliability, completeness and shortness, as they commonly span time lengths of the same order of magnitude or even shorter than the inter-event time of the strongest earthquakes produced by specific seismic sources. In this respect, alternative methods can be proposed for integrating and improving our knowledge of seismogenic processes, and estimating both time-independent and time-dependent occurrence rates of strong earthquakes. We propose the application of physics-based earthquake simulators, requiring the knowledge of a robust geological-geophysical seismogenic model.

Enhanced Tidal Sensitivity of Seismicity Before the 2019 Magnitude 7.1 Ridgecrest, California Earthquake

AbstractEarth's crust is continuously subjected to oscillatory stress perturbations due to the solid Earth and ocean tides. The seismic response to such stress modulations carries information on earthquake physics and crustal properties. Experimental and observational studies suggested but could not demonstrate that the strength of tidal modulation of seismicity increases before large earthquakes. We tested this hypothesis by (a) developing a new, comprehensive 10‐year long earthquake catalog preceding the 6 July 2019 magnitude 7.1 Ridgecrest, CA earthquake, and (b) applied our novel method for extracting a statistical signal of tidal modulation. Our results show enhanced tidal sensitivity of seismicity along the fault starting about 1.5 years before the mainshock, corroborating the hypothesis. This observation suggests that small magnitude earthquakes may be used to gain insight into subtle changes in fault conditions, bringing new promise for studying the earthquake preparation process.

Estimating the economic loss caused by earthquake in Mainland China

In order to estimate the post-earthquake losses in Mainland China, this paper develops a set of economic loss estimation models for Mainland China based on fixed asset data and the damaging information compiled in the Mainland China composite damaging earthquake catalog (MCCDE-CAT). Considering the differences in seismicity and economic development levels across China, these estimation models are developed separately for different sub-regions. Before performing regression analysis, the Human development index (HDI) is used to normalize the economic loss ratio from earthquake occurrence to the present. The robustness and effectiveness of the loss estimation models are verified by separating the loss information in MCCDE-CAT into sample and test data. According to the loss estimation models developed and the normal distribution characteristics of the residuals between modeled and recorded loss data, the probability of different ranges of predicted earthquake economic loss can be determined. Finally, the 2021 Ms 6.4 Yangbi earthquake is taken as an example to demonstrate the application of our developed loss estimation model. The good consistency between the economic loss estimated based on post-earthquake investigations and the predicted economic loss range by our model further indicates the applicability of the model in rapid post-earthquake loss estimation. In the future, the economic loss estimation method will provide scientific guidance in post-earthquake government reconstruction decision-making and international humanitarian assistance. This method is also applicable to disaster loss estimation in any country and region in the world.

The Premodern Descriptive Earthquake Catalogs of von Hoff (1840–1841), Perrey (1845–1850), and Mallet (1853–1855) Under a Magnifying Glass

Abstract The global premodern descriptive catalogs of von Hoff (1840–1841), Perrey (1845–1850), and Mallet (1853–1855), all covering the period from Antiquity to 1842, have been used to populate the preinstrumental section of parametric catalogs since the late 1960s. The earthquake lists of these three authors have been individually analyzed to compile a comprehensive inventory of the sources on which they relied. Conversely to previous analyses and uses that were focused—primarily if not exclusively—on their seismological content, both in the compilation of the inventory and in this article the hundreds of items supplying earthquake records are in the foreground. After having merged these three sets of sources and having obtained a comprehensive list of about 5000 earthquakes and two times more source entries, similarities and differences are evidenced. This comprehensive analysis is meant to catch and explain how the preference given to one source among many available may have affected the interpretation of the collected records and influenced the accuracy and reliability of the earthquake lists by von Hoff, Perrey, and Mallet, and consequently of their contribution to the construction of the global modern parametric earthquake catalogs.

Combining Seismotectonic and Catalog-Based 3D Models for Advanced Smoothed Seismicity Computations

Abstract The new generation seismic hazard maps use 3D seismotectonic fault models, which are more consistent with the actual nature of faults, whereas the classical models based on earthquake catalogs only utilize a 2D representation of the seismicity. Although the former provides more reliable information on seismogenic structures, the latter can deliver trustworthy seismicity rates easily. Therefore, it is necessary to combine both the approaches to create a high-quality seismic hazard assessment model. This study proposes an innovative approach using smoothed seismicity methods that can be advantageous in all contexts with available 3D fault models and high-quality seismic catalogs. We applied our method on the Adriatic Basal Thrust (ABT) in eastern central Italy—a lithospheric-scale active contractional structure with a well-constrained 3D geometric–kinematic reconstruction and a related high-quality catalog. Our new 3D algorithm was applied to smooth the ABT seismicity on the grid, resulting in a 3D earthquake rate model that also provides rupture parameters such as strike, dip, rake, and seismogenic thickness. Our approach is particularly useful for complex seismotectonic settings, such as in cases of lithospheric shear zones, subduction planes, and overlapping multidepth seismogenic volumes.

Earthquake Catalog Processing and Swarm Identification for the Pacific Northwest

AbstractThe Pacific Northwest (PNW) of North America encompasses diverse tectonic settings that can produce damaging earthquakes near population centers. Seismicity in this region is often clustered into aftershock sequences and swarms, and their patterns and frequencies differ across subregions or tectonic regimes. Characterizing the seismicity of the PNW requires a catalog of observed earthquakes. Furthermore, applications with the catalog may require earthquake clusters to be identified and regarded separately. Unlike previous studies, we explicate how to overcome challenges when combining catalogs from different countries, particularly in accounting for duplicate events and other discrepancies. We apply this to merge authoritative catalogs for the United States and Canadian portions of the PNW, along with a third dataset with data quality measures. We also perform a window-based search for earthquake clusters, which then get labeled as possible or definite swarms or aftershock sequences. We further split the catalog into its two primary tectonic regimes. We then study the PNW catalog’s completeness, and the extent to which this varies between the northern and southern parts of the region. We provide a harmonized international PNW catalog with derived variables describing earthquake clustering and tectonic regimes. This entire processing pipeline has also been fully documented and is supported with software, enabling its use in other seismic regions.

The attenuation of macroseismic intensity in the volcanic island of Ischia (Gulf of Naples, Italy): comparison between deterministic and probabilistic models and application to seismic scenarios

In this paper, we tackle the problem of the intensity attenuation at Ischia, a critical parameter in a high seismic risk area such as this volcanic island. Starting from the new revised catalogue of local earthquakes, we select a dataset of 118 macroseismic observations related to the four main historical events and analyse the characteristics of the intensity attenuation according to both the deterministic and probabilistic approaches, under the assumption of a point seismic source and isotropic decay (circular spreading). In the deterministic analysis, we derive the attenuation law through an empirical model fitting the average values of ΔI (the difference between epicentral intensity I0 and intensities observed at a site IS) versus the epicentral distances by the least-square method. In the probabilistic approach, the distribution of IS conditioned on the epicentre-site distance is given through a binomial-beta model for each class of I0. In the Bayesian framework, the model parameter p is considered as a random variable to which we assign a Beta probability distribution on the basis of our prior belief derived from investigations on the attenuation in Italy. The mode of the binomial distribution is taken as the intensity expected at that site (Iexp). The entire calculation procedure has been implemented in a python plugin for QGIS® software that, given location and I0 (or magnitude) of the earthquake to be simulated, generates a probabilistic seismic scenario according to the deterministic or probabilistic models of attenuation. This tool may be applied in seismic risk analyses at a local scale or in the seismic surveillance to produce real-time intensity shake-maps for this volcanic area.

Earthquakes Record Cycles of Opening and Closing in the Enhanced Seismic Catalog of the 2008 Okmok Volcano, Alaska, Eruption

AbstractSeismicity during explosive volcanic eruptions remains challenging to observe through the eruptive noise, leaving first‐order questions unanswered. How do earthquake rates change as eruptions progress, and what is their relationship to the opening and closing of the eruptive vent? To address these questions for the Okmok Volcano 2008 explosive eruption, Volcano Explosivity Index 4, we utilized modern detection methods to enhance the existing earthquake catalog. Our enhanced catalog detected significantly more earthquakes than traditional methods. We located, relocated, determined magnitudes and classified all events within this catalog. Our analysis reveals distinct behaviors for long‐period (LP) and volcano‐tectonic (VT) earthquakes, providing insights into the opening and closing cycle. LP earthquakes occur as bursts beneath the eruptive vent and do not coincide in time with the plumes, indicating their relationship to an eruptive process that occurs at a high pressurization state, that is, partially closed conduit. In contrast, VT earthquakes maintain a steadier rate over a broader region, do not track the caldera deflation and have a larger b‐value during the eruption than before or after. The closing sequence is marked by a burst of LPs followed by small VTs south of the volcano. The opening sequence differs as only VTs extend to depth and migrate within minutes of the eruption onset. Our high‐resolution catalog offers valuable insights, demonstrating that volcanic conduits can transition between partially closed (clogged) and open (cracked) states during an eruption. Utilizing modern earthquake processing techniques enables clearer understanding of eruptions and holds promise for studying other volcanic events.

Seismic Hazard in Greece: A Comparative Study for the Region of East Macedonia and Thrace

Greece is located in one of the most seismically active regions in Europe. Many seismic hazard studies have been performed for various sites around Greece, at a regional or local scale. However, the latest national seismic hazard map, currently used for the seismic design of buildings and infrastructure, was published in 2000 and has not been updated since then. In light of recent advances in seismic source and ground motion modeling, the present study focuses on a comparative Probabilistic Seismic Hazard Assessment (PSHA) for the region of East Macedonia and Thrace (EMTH), located in Northern Greece. Various seismic source models are implemented and compared against an updated earthquake catalog to form the necessary source model logic tree. The ground motion logic tree is composed of Ground Motion Prediction Equations (GMPEs), which have been proven suitable for implementation in Greece. PSHA results are presented for the most important cities of East Macedonia and Thrace in a comparative way, which highlights the variability of the seismic hazard among the various seismic source models. An updated seismic hazard map of the study area is proposed, and a comparative disaggregation analysis is performed to estimate the earthquake scenarios with the largest contribution to the seismic hazard.

Penghitungan Peak Ground Acceleration (PGA) di Desa Kuta Menggunakan Persamaan Empiris pada Gempabumi 19 Agustus 1977 (Mw = 8.3)

The August 19, 1977 earthquake was one of the major earthquakes that ever occurred in the Nusa Tenggara area with an impact on the island of Lombok, one of which was in Kuta Village. The purpose of this research is to determine the empirical equation that is suitable for use in Kuta Village to calculate the Peak Ground Acceleration (PGA) value in the form of a distribution map. The PGA value can provide an overview of the damage to buildings caused by the earthquake. The PGA calculation uses several empirical equations of Donovan, M.C.Guirre, Esteva, and Oliviera. Earthquake data was obtained through data released from the USGS and the destructive earthquake catalog. The PGA value obtained with the Donovan empirical equation is a PGA value that is close to the value from the results of the BMKG Shakemap scenario with the MMI III scale. This earthquake did not cause damage to the Kuta Village area but damage was caused by the tsunami after the earthquake occurred. Keywords: Sumba Earthquake, Kuta Village, Maximum Ground Acceleration, Empirical Equation.

Estimation of Flores Sea Aftershock Rupture Data Based on AI

The earthquake catalog notes that there have been earthquakes with Mw > 7 that hit the Flores area, three of which occurred in the Flores Sea in 1992, 2015, and 2021. Revealed that the seismic activity of Eastern Indonesia is thought to be influenced by the isolated thrust fault segment of the island of Flores and the island of Wetar. The study of the rising fault segment on Flores Island and Wetar Island helps in further understanding the fault behavior, earthquake pattern, and seismic risk in the Flores Sea region. In earthquakes with giant magneto, an aftershock can occur due to the interaction of ground movements. This research analyzes and compares the data from the evaluation of the classification algorithm and the regression algorithm. The initial stages of this research include requesting IRIS DMC Web Service data. The data is then subjected to a cleaning process to obtain the expected feature extraction. The next stage is to perform the clustering process. This stage is carried out to label dependent data by adding new features as data clusters. The following procedure divides the validation value, which consists of training and test data. The estimation results show that the classification algorithm's evaluation value is better than that of the regression algorithm. The evaluation value of several algorithms indicates this, with an accuracy rate between 80% and 100%.

Comparative Probabilistic Seismic Hazard Analysis for Sakarya

Sakarya province can be significantly affected by earthquakes on the North Anatolian Fault. Earthquake hazard includes some uncertainties. Earthquake catalog data is needed for probabilistic earthquake hazard calculations. In addition to current catalog information, existing attenuation relationships, including earthquake characteristics for the region, should be developed or their suitability checked. For this purpose, an earthquake hazard analysis was carried out for the Serdivan, Erenler, Adapazarı, and Arifiye districts of Sakarya by using the EMME (Earthquake Model of the Middle East Region) data catalog, which was carried out on a global scale and using the ASK14 model from the NGA-West2 equations. CRISIS software was used for analysis. As a result of the study, it was concluded that the evaluation of ground effects in these regions is an essential requirement.

Global Characteristics of Observable Foreshocks for Large Earthquakes

AbstractForeshocks are the only currently widely identified precursory seismic behavior, yet their utility and even identifiability are problematic, in part because of extreme variation in behavior. Here, we establish some global trends that help identify the expected frequency of foreshocks as well the type of earthquake most prone to foreshocks. We establish these tendencies using the global earthquake catalog of the U.S. Geological Survey National Earthquake Information Center with a completeness level of magnitude 5 and mainshocks with Mw≥7.0. Foreshocks are identified using three clustering algorithms to address the challenge of distinguishing foreshocks from background activity. The methods give a range of 15%–43% of large mainshocks having at least one foreshock but a narrower range of 13%–26% having at least one foreshock with magnitude within two units of the mainshock magnitude. These observed global foreshock rates are similar to regional values for a completeness level of magnitude 3 using the same detection conditions. The foreshock sequences have distinctive characteristics with the global composite population b-values being lower for foreshocks than for aftershocks, an attribute that is also manifested in synthetic catalogs computed by epidemic-type aftershock sequences, which intrinsically involves only cascading processes. Focal mechanism similarity of foreshocks relative to mainshocks is more pronounced than for aftershocks. Despite these distinguishing characteristics of foreshock sequences, the conditions that promote high foreshock productivity are similar to those that promote high aftershock productivity. For instance, a modestly higher percentage of interplate mainshocks have foreshocks than intraplate mainshocks, and reverse faulting events slightly more commonly have foreshocks than normal or strike-slip-faulting mainshocks. The western circum-Pacific is prone to having slightly more foreshock activity than the eastern circum-Pacific.

Probabilistic seismic hazard and risk assessment of Mizoram, North East India

This paper presents seismic hazard and risk assessment for the state of Mizoram based on a classical probabilistic seismic hazard analysis and event-based probabilistic seismic risk analysis. For the seismic hazard estimation, analysis has been performed considering the areal source model, fault zone polygon, and smoothed gridded seismicity model. The earthquake activity rates for these source zones and smoothed gridded seismicity sources are estimated from the homogenized and declustered earthquake catalogue. The logic tree framework is applied in the seismic source models and Ground Motion Prediction equations (GMPEs) to account for the epistemic uncertainties. Five Next-generation attenuation (NGA) GMPEs for the active shallow region and three GMPEs for the Indo-Burma subduction zone have been used to evaluate the hazard at the reference rock condition (Vs30 ​= ​760 ​m/s). Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) at 0.2 s and 1s are estimated for each eight districts headquarters of Mizoram for a 2% and 10% probability of exceedance in 50 years. The hazard curves and Uniform Hazard Spectra (UHS) are also presented. For seismic risk analysis, building exposure data are based on digitized building footprint and 2011 Housing Census data of India. All the buildings are classified into three classes, and seismic vulnerability functions are assigned to each building class. The area per building class is assigned from the digitized footprint. Building replacement costs per square meter have been chosen based on expert input and values identified from past study. Lastly, the study conducted a seismic risk analysis using the Open Quake-engine's probabilistic event-based methodology to estimate risk metrics at the district level, such as average annual losses and probability curves for loss exceedance. The study's findings provide valuable insights into the most high-risk areas, the building construction types that are most vulnerable to seismic activity, and the anticipated economic losses in the state of Mizoram. These results can serve as a guide for local government authorities in developing future city plans and implementing earthquake risk mitigation strategies.

Penghitungan Peak Ground Acceleration (PGA) di Desa Kuta Menggunakan Persamaan Empiris pada Gempa Bumi 19 Agustus 1977 (Mw = 8.3)

The August 19, 1977 earthquake was one of the major earthquakes that ever occurred in the Nusa Tenggara region with an impact on the island of Lombok, one of which was in Kuta Village. The purpose of this research is to determine the empirical equation that is suitable for use in Kuta Village to calculate the Peak Ground Acceleration (PGA) value in the form of a distribution map. The PGA value can provide an overview of the damage to buildings caused by the earthquake. The PGA calculation uses several empirical equations of Donovan, M.C.Guirre, Esteva and Oliviera. Earthquake data obtained through data released from the USGS and the destructive earthquake catalog. The PGA value obtained with the Donovan empirical equation is a PGA value that is close to the value from the results of the BMKG Shakemap scenario with the MMI III scale. This earthquake did not cause damage to the Kuta Village area but damage was caused by the tsunami after the earthquake occurred.