Series Of Earthquakes Research Articles

Seismic slip channeling along the East Anatolian Fault illuminates long-term supercycle behavior

The two Mw > 7.5 earthquakes that struck the East Anatolian Fault (EAF), Türkiye, in 2023 caused more slip than expected, indicating that they were potentially part of a supercycle, in which the occurrence probability of a large earthquake is determined by accumulated strain rather than time since the last large earthquake. Here, we show two potential supercycles along the EAF, analyzing earthquakes from the last two millennia. Within each supercycle, seismic ruptures originated in the northeast and progressively spread southwestward with an increasing number of earthquakes until a new supercycle began with another large earthquake in the northeast. To understand the supercycle behavior, we analyze the aftershock sequences of the four most recent Mw≥6.1 mainshocks (2010–2023). This series of earthquakes progressed southwestward, characterized by an increasing diversity of focal mechanisms and a heightened dispersion of epicenters across a branched seismotectonic environment. Earthquakes in the northeast exhibit spatial and kinematic channeling along the master fault surface, effectively transferring slip southwestward and there potentially triggering dispersed and heterogeneous earthquakes. This spatiotemporal pattern seems connected with varying levels of a presumably-innate property of fault sections or regions, ruling the process of seismic slip channeling, which could also explain the behavior of long-term supercycles.

Estimation of frequencies and Q-factors of Earth’s low-frequency toroidal normal modes using strain data

In the study, estimations of the parameters of three low-frequency toroidal modes 0T2, 0T3, and 0T4, excited by the 13 largest earthquakes of the 21st century, were carried out. The etimations were obtained using the data from the Baksan Laser Interferometer–Strainmeter of SAI MSU. Using an adaptive spectral algorithm, estimates of the modes’ frequencies were obtained, and they were compared with the PREM model. Significant deviations in the frequency estimates of the 0T4 mode for a series of earthquakes were found, showing their possible connection with local inhomogeneities in the values of the speed of shear waves and the Earth’s density in the upper mantle. The splitting of the 0T2 mode due to Earth’s ellipticity and rotation was studied, with frequency estimates of singlets excited after catastrophic earthquakes in Sumatra, Japan, and Chile obtained. An evaluation of the Q-factors of the low-frequency toroidal modes was performed using three different methods.

GEOTECHNICAL INVESTIGATIONS FOR SCHOOL CONSTRUCTION

A series of earthquakes that commenced on December 28, 2020, resulted in extensive material damage within a 50-60 km radius from the epicenter, located near the City of Petrinja. Due to the significant structural damage sustained by the building of Petrinja Primary School I, a decision was made to construct a new school building. The construction of the new school began in 2022 and was completed in 2023. This study presents the findings of geotechnical investigations conducted at the site of the new school, which included five static cone penetration tests (CPTu), two dynamic probing heavy tests (DPH), one Marchetti dilatometer test (DMT), and two profiles of multi-channel analysis of surface waves (MASW). The geotechnical investigations resulted in the development of a soil profile consisting of eight distinct zones. Recommendations for the foundation design of the new building have been provided, alongside an assessment of the risk of soil liquefaction. The potential for liquefaction has been identified within zone 4, which comprises clayey sands at depths ranging from 4 to 6 meters.

Active Fault Interaction in the Eastern Betic Cordillera: A Model of Coseismic and Postseismic Stress Transfer Following Historical Earthquakes in SE Spain

AbstractThe Spanish historical earthquake catalog reveals a significant number of destructive earthquakes (Mw 6.0) that have occurred along the Eastern Betic Shear Zone (EBSZ), a major active fault system at the Eastern Betic Cordillera. However, during the last century, seismic activity in this region has been characterized by the absence of large‐magnitude events, complicating yet underlining the importance of understanding active fault interaction in the EBSZ. In this work, we focus on the northeastern half of the EBSZ and apply a similar method to Yazdi et al. (2023, https://doi.org/10.1029/2023tc007917). We model a series of consecutive earthquakes ( VII; Mw 5.0) between the and centuries occurring along the Alhama de Murcia, Carrascoy and Bajo Segura faults, and assess their coseismic impact as well as explore the evolution of Coulomb stress changes due to the postseismic viscoelastic relaxation on the surrounding faults. Our results support a stress‐triggering connection between subsequent events and shed light on identifying the responsible faults for some. Our findings indicate that 1673 Mw 6.0 Orihuela and 1674 Mw 6.2 Lorca earthquakes, seemingly unrelated, could have both contributed to the forthcoming Mw 5.0 earthquake clustering along the Carrascoy fault. We show that attributing the 1829 Mw 6.6 Torrevieja earthquake to the Bajo Segura fault better describes the occurrence of earthquake sequences between the mid‐ and early centuries. Finally, we propose the Alhama de Murcia and the Carrascoy faults as responsible initiators for the early ‐century earthquake sequence in the Segura Medio valley. These findings provide valuable insights for seismic hazard modeling in the region.

Investigation of the effects of Kahramanmaraş earthquake series on Cyprus Arc, Dead Sea fault, Hatay regions and stations close to two earthquakes epicenters

In various parts of the globe, there have been several earthquakes of a modest size. Monitoring the change of the points over time is a key component of typical techniques for extracting dynamic responses. This technique was unable to completely extract all of the earthquake’s dynamic properties. The GNSS precise point positioning (PPP) may be a useful tool for obtaining values of the point’s displacement that are more exact up to millimeters, which can help to overcome these flaws and evaluate the seismic wave of such earthquakes. Ultimately, PPP is a crucial tool for getting the precise observations. In this study, Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) approach to analyze the station’s displacement components and the station’s heights in periods from the two Kahramanmaraş earthquakes. The earthquake sequences that occurred in Turkey’s Kahramanmaraş in 2023 is an example of complicated faulting brought on by interactions between three plates close to the Hatay Triple Junction (HTJ). While the relative plate movements in this area are minimal (usually less than 10 mm/year), even sluggish plate motion zones may nevertheless see earthquakes that are quite destructive. Due to the three-plate system’s unusual geometry, a number of large earthquakes with very varied fault orientations were active throughout this series. A 7.8-magnitude earthquake happened on February 6, 2023 in southern Turkey, close to Syria’s northern border. A magnitude 7.5 earthquake, situated about 95 kilometers to the southwest, was occurred nine hours after the first one. The first earthquake was as big as the most powerful one ever recorded there in 1939 and was the most catastrophic to strike earthquake-prone Turkey in more than 20 years. In this study, the effects of two earthquakes in Kahramanmaraş were investigated on the Cyprus Arc, the Dead Sea fault, Hatay and the points close to two earthquakes zone. In the obtained results, it was computed that the greatest horizontal displacement occurred at the HAT2 station with 68.97 cm.

Structural features and tectonic activity of the Weihe Fault, central China

Abstract The study of tectonic activity holds great significance in assessing historical and modern seismic risks. The Weihe Graben is a significant intracontinental graben system in China, with numerous active faults that have caused a series of earthquakes, including the Huaxian great earthquake (M ∼ 8.5) in 1556 with approximately 830,000 deaths. Despite the obvious spatial relationship between the Weihe fault (WF) and these earthquakes, detailed research on the fault is still lacking. Various techniques including remote sensing images, digital elevation model, shallow seismic lines, trench excavation, drilling sections, and optically stimulated luminescence dating, have been utilized to obtain the following results: (1) The WF passes through the scarp of the Weihe River terrace in the north of Xianyang and can be divided into east and west sections at Jinjia village; (2) The WF is a normal fault that strikes northeast and dips south with a dipping angle of 65°–75°; (3) The fault has been active during the Holocene; (4) The vertically offset and dating results suggest that the fault activity has gradually decreased since the late Pleistocene, and the vertical slip rate during the Holocene is only 0.04–0.13 mm/year.

Deformation and displacements of Earth’s surface in Turkish earthquakes era in February 2023 by geodesy data

The work analyzes the connection between a series of Turkish earthquakes in February 2023 and coseismic displacements and deformations on the Earth's surface. In areas of seismic rupture during the five days, there are recordings of three earthquakes on February 6 with magnitudes 7.8, 6.7, 7.5 and then for 5 days period – 42 events of magnitude 4.5–6.0. This work analyzed data obtained by various geodesy methods in the epicentral region. Coseismic effects in a 300 kilometers zone, covering a significant part of the East Anatolian Fault, are considered. Relative displacements up to 6 m have been recorded, with an average value 4 m. When for studying far-field effects, we used GPS network data from 27 international stations, of which seven stations located in Turkey. For the closest to the epicenters of the main aftershock on February 6, 2023, MERS station received coseismic 3D displacements up to 20 mm. The displacement and deformation fields have been constructed according to IGS data. Rates of coseismic deformations in the far zone reach up 10–8 , which is an order of magnitude higher than the background values of 10–9 . Post-seismic horizontal and vertical displacements rates of the Earth's surface in areas of Turkey, located to the southwest of the earthquake epicenters can be associated with floods. A study of displacements rates and deformations of the territory was carried out Turkey and its surroundings in the era of 2017–2023. Highlighted decrease displacement rates two years before seismic activation in 2023. The resulting picture of displacement and deformation rates reflects a current processes in the territory located on the borders of Anatolian Block and tectonic plates: Eurasian, Arabian, and African.

Experimental study on the rupture behaviors of orthogonal faults: effects of stress state and rupture initiation location

Summary Fault rupture dynamics is expected to be significantly affected by the geometry of fault system, especially for orthogonal faults. However, the rupture behaviors of orthogonal faults especially the coseismic interactions are far from fully understood. Here, we present experimental results from a series of laboratory earthquakes to elucidate the effect of the stress state and initiation location on the rupture behaviors of orthogonal faults. Our results reveal a phase diagram of rupture behaviors of orthogonal faults, which is collectively controlled by stress state and rupture initiation location. For events initiating from the main fault, the rupture cannot jump to the branch, which may be due to the clamping effect or the inhibited shear stress accumulation on the branch. On the contrary, events initiating from the branch can persistently trigger ruptures of the main fault. This difference highlights the directional effect associated with the rupture of orthogonal faults. Further, the rupture length of triggered ruptures on the main fault is controlled by the stress state of the fault system. With the increase of the ratio between the shear stress and normal stress, the rupture length of the main fault increases. Our results reproduce the rupture behaviors of orthogonal faults, which may provide insights into the rupture characteristics of natural earthquakes.

“We ran outside and waited for it to come”: Resident experiences in response to a false earthquake early warning

Ridgecrest, CA, experienced the Searles Valley earthquake sequence in 2019 and a “false” earthquake alert in 2020, providing a unique opportunity to examine the effects of earthquake experience on future responses to informational cues to action (i.e., earthquake alert), as well as reactions to a “false” alert. We conducted in-depth interviews with 41 residents using the protective action decision-making model as a theoretical framework. Interviewees reported a variety of environmental cues that signaled the onset of an earthquake, including sensing a foreshock, hearing the earth rumble, hearing objects fall to the floor and break, and observing unusual animal behavior. Fewer individuals received social cues to action. More individuals reported performing “drop, cover, and hold on,” and fewer reported standing in a doorway in response to the 2020 alert than had done so in the prior 2019 earthquake. Several respondents reported maintaining protective actions well after the “false” alert was issued, and many waited more than 5 min before determining there was no threat present. Prior experience of the 2019 earthquake series affected perceptions of the earthquake alert and what actions to take; however, there was limited knowledge of how the ShakeAlert system worked to monitor, detect, and model earthquakes via earthquake early warning to persons at risk. Findings indicate there is a need for additional public education about ShakeAlert-powered earthquake early warning, including how far in advance one can expect to receive an alert, as well as the protective actions one should take and when to take them.

Magnetic and Ionospheric Effects of a Series of Strong Earthquakes on April 2‒3, 2024 (Taiwan)

Magnetic and Ionospheric Effects of a Series of Strong Earthquakes on April 2‒3, 2024 (Taiwan)

Anomalous geomagnetic activities before the Karangasem - Bali, Indonesia earthquakes on December 13, 2022

Abstract A series of earthquakes occurred on Bali Island, Indonesia, on December 13, 2022. The United States Geological Survey (USGS) recorded four shallow earthquakes around Karangasem - Bali with magnitude (M) > 4 at that time. The largest was the M 5.2 earthquake, which occurred at 10:38:21.67 UTC with 10 km of depth. We analyzed the anomalous geomagnetic activities during these earthquakes by utilizing the geomagnetic data from the Bayan geomagnetic station located on Lombok Island, less than 100 km from the earthquake’s epicenters. We conducted the polarization ratio analysis by applying the Fast Fourier Transform (FFT) on the five hours of night geomagnetic data (16:00 - 21:00 UTC). The spectral power values of X, Y, and Z geomagnetic data at frequencies 0.04 - 0.06 Hz were calculated and compared with the disturbance storm time (Dst) to find their correlation. The Pearson correlation analysis indicates that they are significantly uncorrelated. Finally, we calculated the Sz/Sg to analyze the geomagnetic anomalies and found them 6 - 11 days before the earthquakes at frequencies 0.04 - 0.06 Hz. We consider that these anomalies are possibly caused by the M 5.2 earthquake since it had the highest magnitude, Es, and Kls values.

<p>A Catalogue of Historical and Instrumentally-Recorded M<sub>s</sub> ≥ 7 Earthquakes in Taiwan</p>

A catalogue of forty-nine instrumentally-recorded earthquakes with magnitudes ≥ 7 in Taiwan from 1906 to date is compiled from regional and international catalogues and literature. Included also are seven historical earthquakes that occurred from 1792 to 1867. The earthquake magnitude is the surface-wave magnitude, Ms. The moment magnitude, Mw, is also evaluated either from Ms or obtained from related documents. Except for one event, Mw is smaller than or equal to Ms. There are the ‘doublets’, ‘triplets’, and ‘quadruplets’ in these earthquakes. The spatial distribution of epicenters shows that most of the events occurred in offshore eastern Taiwan and only a few inland events happened in western Taiwan. The shortest inter-occurrence time between two consecutive events is less than 1 day; while the longest one is 5742 days between No. 47 event and No. 48 event. The inter-occurrence time somewhat increases with time. The time series of earthquakes shows irregular recurrence behavior with aperiodicity, fractality, and a weak memory effect. The damage produced by earthquakes is much higher from inland events (mainly in western Taiwan) than from offshore ones.

Investigation of Liquefaction in Balaroa, Petobo, and Jonooge (Central Sulawesi, Indonesia) Caused by the 2018 Palu Earthquake Sequence

The liquefaction that occurred in the city of Palu on September 28, 2018, was caused by a series of significant earthquakes that took place in a relatively short time around 25 minutes after the main earthquake of magnitude 7.5. This event was followed by aftershocks of magnitudes 6.4, 6.2, and 6.1. The magnitude 6.2 aftershock occurred at 10.16 UTC, while the magnitude 6.1 aftershock occurred at 10.25 UTC. These were both located very close to the liquefaction locations in Balaroa, Petobo, and Jono Oge. We investigated the mainshock and the three aftershocks using the NCEER method based on Vs30 measurements and data from the drill liquefaction locations at Balaroa, Petobo, and Jono Oge. We found that the liquefaction was not only caused by the main earthquake but also by the subsequent aftershocks that occurred within 25 minutes after the mainshock.

InSAR- and PCA-Based Inversion Reveals the Surface Deformation and Earthquake Sequence in the Weiyuan-Rongxian Shale Gas Field

In recent years, the rapid expansion and development of the shale gas industry in the Sichuan Basin has coincided with a series of unexpected moderate-sized earthquakes. Given that the Sichuan Basin is situated within a stable interior block, the focal mechanism of the 2019 earthquake sequence (ML4.7, ML5.4, and ML5.2) in the Weiyuan-Rongxian area remains a subject of debate. In this study, we propose a joint InSAR- and PCA- based inversion method utilizing the distributed Mogi model to investigate the spatial-temporal characteristics of a gas reservoir and evaluate the induced Coulomb stress change. The surface deformation derived from Sentinel-1 data between 2015 and 2021 was consistent with the spatial distribution of production wells, and it correlated with the temporal changes in reservoir volume associated with the shale gas operating process. The Coulomb stress loading on the regional faults suggests that human activities associated with shale gas operation likely triggered the three moderate earthquakes. Furthermore, our results indicate Coulomb stress loadings of 10 kPa, 15 kPa, 5 kPa, 3 kPa, and 87 kPa on the Dongxingchang fault, Gaoqiao fault, Dayaokou fault, Niujingao fault, and Lijiachang fold, respectively. Consequently, fluid injection and extraction during shale gas development could be contributing to the elevated seismic activity in the Weiyuan-Rongxian area.

Numerical simulation of fault activity in the Qilian tectonic belt and dynamic background of Menyuan earthquake series

Some faults in the Qilian tectonic belt are seismogenic areas for strong earthquakes, including the western section of the Lenglongling fault, which frequently occures moderate-strong Menyuan earthquakes. In this study, using GPS velocity data of 1991–2015 as the boundary constraints, a three-dimensional viscoelastic finite element dynamic model is constructed by comprehensively considering the regional dynamic environment, crust-mantle transverse-longitudinal inhomogeneity, and spatial spreading of a complex fault system. The objective is to investigate the long-period characteristics of fault movement and stress change in the Qilian tectonic belt caused by tectonic loading, and to discuss the seismogenic conditions of the Menyuan earthquakes. The results show that the annual change of long-period movement and stress of the major faults in the Qilian Mountain tectonic zone are characterized by significant segmentation. Due to its unique geometric bend morphology, the western section of Lenglongling fault has a low movement rate, significant slip deficit and high shear stress accumulation, which are conducive to the gestation and occurrence of earthquakes. Furthermore, the seismogenic area of the Menyuan earthquake series is jointly subjected to NE-SW compressive and NW-SE tensile stress fields, and the maximum shear stress and elastic strain energy accumulate faster than in the surrounding areas. Overall, the western section of the Lenglongling fault has a strong dynamic background and favorable conditions for the frequent occurrence of the Menyuan earthquake series.

Midcrustal moderate-size earthquake occurrence in paleovolcanic structures off Jeju Island, South Korea

A series of midcrustal moderate-size earthquakes occurred in the Korean Peninsula recently. A midcrustal ML4.9 strike-slip earthquake with a fault-plane strike in N-S occurred on December 14, 2021 at the southwestern offshore region of Jeju Island, South Korea. The fault plane orientation and slip sense (faulting mechanism) hardly conform with the regional stress field. The deep focal depth and N-S directional strike-slip motion require transient changes in the medium properties and stress field. Strong ground motions of the midcrustal earthquake induce preferential dynamic stress changes in NE-SW direction, triggering subsequent aftershocks in NE-SW-directional adjacent faults. Both the static and dynamic stress changes caused by the mainshock contribute to the aftershock sequence. The number and focal depths of aftershocks decrease with distance from the mainshock. The different fault-plane orientations between the mainshock and aftershocks suggest earthquake nucleations in independent fault structures. The mainshock occurred in aseismic midcrustal paleovolcanic structure on the outskirt of a high seismicity region. The ML4.9 earthquake suggests possible nucleation of earthquake in seismically-inactive paleotectonic structures, successively incurring aftershocks conforming to the ambient stress. The mainshock and aftershocks suggest that paleotectonic structures may behave as source structures to spawn earthquakes.

Field observations on the damage to road bridges after the 2023 Turkey Earthquake

A series of large-scale earthquakes occurred on February 6 in southern Turkey. The authors had the opportunity to join the Japan Disaster Relief (JDR) Expert Team and visit several damaged areas in Turkey from March 10 to 12, 2023. This article highlights damage cases of a road tunnel and several road bridges the authors observed around Antakya, Nurdağı, and Malatya. From the features of the observations, this article discusses the following three items for further study in the seismic design of road bridges: (1) seismic details for robustness, (2) seismic responses of bridges with longer natural periods, and (3) post-event inspection.

Investigation of seismic damage to existing buildings by using remotely observed images

A prolonged and highly destructive seismic sequence struck Central Italy, spanning from August 24, 2016, to January 2017. This series of earthquakes resulted in widespread structural failures and extensive damage across four regions along the Apennines: Lazio, Umbria, Marche, and Abruzzo. In the context of this study, based on post-earthquake remotely observed damages data, we conducted an in-depth empirical examination of the vulnerability of various types of buildings, including reinforced concrete, masonry, and steel structures. These valuable data, accessible through a Google Street View application, furnished critical insights into building locations, characteristics, and spatially observed patterns of damage before and after the seismic events. We undertook a meticulous review and comparison of this extensive dataset to ensure its consistency with prior earthquake observations, fragility functions, and relevant scientific literature. Our research involved a comprehensive examination of selected structures by combining post-earthquake inspections and visual assessments using Google Street View. This comprehensive study allowed us to compare similar buildings with and without damage, generating significant statistical insights into the types of structural pathologies that lead to localized and widespread damage, as well as instances of structural collapses or domino effects. Furthermore, we propose a preliminary glimpse at the power of Machine Learning techniques into earthquake risk assessment. We suggest that this approach could enhance the robustness and accuracy of modeling procedures, which are essential when addressing such complex challenges.

Organized professional response to a large-scale disaster: Earthquakes in Türkiye

AbstractIn February 2023, a series of earthquakes with high magnitudes affected 11 cities in Türkiye, a region with a population of over 13 million. With more than 50000 recorded deaths and more than 3 million survivors replaced, rescue and recovery efforts were challenging. The Psychiatric Association of Türkiye (PAT) immediately launched a “Disaster and Crisis Management,” which urgently formed and installed a program for psychosocial support and psychiatric care. The program included immediate, medium, and long-term actions. Hundreds of recruitments followed a call for volunteers for on-site and online support. An online “Earthquake and Mental Health” library was launched immediately, and a series of webinars on psychological first aid and disaster psychiatry were organized in the first two weeks. Furthermore, in three major cities, separate interactive meetings where question and answer sessions with trauma experts have been possible were held weekly with smaller groups. Almost a hundred volunteer PAT members served in the region in the first few months after the earthquake. All colleagues in the field, including those who survived the earthquakes, benefited from the resources of the PAT for their needs in housing, food, and mobilization. Starting from the first days, the PAT organized regional centers for coordination, which required financial resources and staff. The demand was high and could only be met with close collaboration with the Turkish Medical Association and the financial support obtained from international agencies, WPA, and other national psychiatric associations. The PAT started an online support system with technical support from a professional company, targeting healthcare professionals and first responders in the earthquake area. Volunteering psychiatrists provided appointment slots, rendering the system available 12 hours a day, seven days a week. With time, as the national healthcare delivery recovered, the PAT activities transformed into coordination, education, and supervision. Furthermore, the psychiatry residency training, which was interrupted due to the disaster, has been supported through a nationwide mentorship program launched by the PAT. The experience of the Psychiatric Association of Türkiye with disasters paved the way for an organized response, which was made possible through national and international solidarity.Disclosure of InterestNone Declared

Socio-Economic Development of Tibet in the 11th Five-Year Plan (2006–2010). Part 9

The 11th Five-year Plan of the People's Republic of China was an important stage in the socio-economic development of both the whole of China and the TAR in its composition. The plan set an annual GDP growth rate of 7.5 %, which actually exceeded 10 %. Tibet, on the other hand, was developing at a rate of more than 12 % per year. During the five-year plan, Tibet experienced many serious trials: a series of powerful earthquakes that claimed thousands of lives. In 2008, when China was preparing to host the Olympic Games in Beijing in August, Western intelligence agencies provoked an uprising in Lhasa on March 18. The leaders of France (in 2008) and the United States (in 2010) distinguished themselves by provocations against China, meeting with the Dalai Lama, despite the vigorous objections of the Chinese authorities. Nevertheless, Britain officially recognized Tibet for the first time as an autonomous region within the PRC. Significant achievements have been made in the development of transport in the region and especially aviation. Tibet remained one of the twelve least developed western regions of the People's Republic of China, but its economy continued to develop dynamically. The authority of Tibet in the world community has significantly increased, one of the manifestations of this was the great success of Tibet at the world Exhibition in Shanghai in 2010.