Potential Earthquake Research Articles

Rupture propagation on heterogeneous fault: Challenges for predicting earthquake magnitude

<p indent="0mm">Predicting magnitudes and ground motion of future strong earthquakes on seismogenic faults holds critical implications on seismic hazard zonation and mitigation. Although present approaches to seismic hazard assessment can effectively identify potential regions to host strong earthquakes, it remains extremely challenging to accurately predict future earthquake magnitudes because of various heterogeneities of fault zones, such as fault geometry, medium structure, and frictional properties. In this work, we review a few aspects that play important roles in earthquake rupture propagation and extent, so as to determine the final magnitude of earthquakes. Under the condition of heterogeneous stress distribution on faults, the final magnitude of earthquakes as well as shallow slip distribution depends on where the rupture initiates. As shown in recent numerical models of dynamic rupture simulations, different hypocenters with similar stress level can lead to completely different rupture scenarios, some of which may significantly break the ground whereas others may be buried underground. Such findings shed critical light on seismic hazard preparation, because surface-breaching ruptures can lead to severe damage as vividly evidenced by the 2022 Menyuan <italic>M</italic>_w 6.7 earthquake. To date, we cannot predict future hypocenter locations according to our knowledge of earthquake nucleation and therefore future relevant investigations are highly demanded. Furthermore, the size of seismogenic zone on strike-slip faults controls whether ruptures may become “break-away” to form large earthquakes or stop spontaneously as “self-arresting” of moderate magnitude events. Observations show that aspect ratios between rupture length and down-dip width of dip-slip earthquakes are usually no more than 8. In contrast, the length/width ratios of strike-slip earthquakes may rise to 40 and have a drastic change around the rupture width of <sc>~10 km.</sc> Intrinsic mechanism of such variation in strike-slip earthquakes is attributed to the energy release rate of rupture fronts, which is controlled by the down-dip width. As such, high-resolution constraints on down-dip seismogenic width can be used to estimate the magnitude of future earthquakes on strike-slip faults. Moreover, fault zone structure significantly affects rupture directivity and slip extents. For instance, low-velocity fault zones may promote rupture propagation and thus enlarge the earthquake magnitude. Given the rapid development of seismic observations and seismic imaging techniques, high-resolution fault zone structure can be obtained from data recorded by dense arrays, including nodal network and the newly developed distributed acoustic sensing (DAS) arrays. Integrating with laboratory results of rheology from samples representing crustal rocks, the near-fault high-resolution seismic structure can be converted into rheological properties on faults, which can then be used to outline asperities for future earthquakes. This may provide a critical step to link seismic structure to earthquake potential, as the outlined asperities can be further used to derive rupture scenarios and earthquake magnitudes. To advance our understanding on this front, future work may integrate multiple sources of observations and modeling. Conducting rupture simulations with constraints from geodetic and seismic measurements, as well as laboratory frictional experiments, can be helpful in exploring potential earthquake magnitudes. By considering heterogeneities on faults with reasonable constraints, the numerical models can be useful for investigating the probable hypocenter locations of large earthquakes. Thus, the numerical results may support future near-field observations to improve monitoring of nucleation and development of future large earthquakes. Furthermore, the ground motions generated from the numerical models can also fill the data gap of near-field observations of large earthquakes and provide critical support for physics-based seismic hazard assessment.

Theoretical Correlations Between the Cumulative Absolute Velocity and Performance Point for a Seismic Analysis of Framed Structures

Abstract The present paper investigates the effect of the harmfulness of a potential earthquake on structural and seismic risks. It takes into account the magnitude, epicentral distance, and pseudo depth at the hypocenter as well as the soil classification in order to generate synthetic seismic motions to be considered as signal inputs for a structural seismic analysis. The most typical typology of dwellings and buildings that are widely existing in Algeria, i.e., a reinforced concrete frame structure, is considered for the case study. The results show that the theoretical models developed in this study are able to predict the performance point (spectral displacement) according to the cumulative absolute velocity. They also show that(CAV-Sd) (Sd being the spectral displacement of the performance point defined by a pushover analysis) is slightly influenced by the value of the ultimate displacements of the structures and the soil parameters (shear velocity Vs).

Swarm-TEC Satellite Measurements as a Potential Earthquake Precursor Together With Other Swarm and CSES Data: The Case of Mw7.6 2019 Papua New Guinea Seismic Event

On May 14, 2019, a strong Mw = 7.6 shallow earthquake occurred in Papua New Guinea. This paper explores for the first time the analysis of total electron content (TEC) products measured for 6 months by GPS antenna onboard Swarm satellites, to detect possible seismo-ionospheric anomalies around the time and location of the above-mentioned earthquake. The night-time vertical total electron content (VTEC) time series measured using Swarm satellites Alpha and Charlie, inside the earthquake Dobrovolsky’s area show striking anomalies 31 and 35 days before the event. We successfully verified the possible presence of concomitant anomalous values of in situ electron density detected by the new Chinese satellite dedicated to search for electromagnetic earthquake precursors [China Seismo-Electromagnetic Satellite (CSES)-01]. On the other hand, the analysis of VTEC night time measured by Swarm Bravo shows gradual and abnormal increase of the VTEC parameter from about 23 days before the earthquake, which descends 3 days before the earthquake and reaches its lowest level around the earthquake day. We also analyzed the time series and tracks of other six in situ parameters measured by Swarm satellites, electron density from CSES, and also GPS-TEC measurements. As it is expected from the theory, the electron density anomalous variations acknowledge the Swarm VTEC anomalies, confirming that those anomalies are real and not an artifact of the analysis. The comparative analysis with measurements of other Swarm and CSES sensors emphasizes striking anomalies about 2.5 weeks before the event, with a clear pattern of the whole anomalies typical of a critical system as the earthquake process is for Earth. A confutation analysis outside the Dobrovolsky area and without significant seismicity shows no anomalies. Therefore based on our study, the VTEC products of Swarm satellites could be an appropriate precursor aside from the other measured plasma and magnetic parameters using Alpha, Bravo, and Charlie Swarm and CSES satellites that can be simultaneously analyzed to reduce the overall uncertainty.

Pliocene–Quaternary seismogenic faults in the inner Northern Apennines (Valdelsa Basin, southern Tuscany) and their role in controlling the local seismicity

AbstractPliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.

Rethinking earthquake-related vulnerabilities of historic centres in Italy: Insights from the Tuscan area

Earthquakes pose a looming threat to human life and habitats, as well as the large-scale preservation of urban cultural heritage assets located in historic centres. These areas, worldwide perceived as cultural, social and economic resources for communities, are experiencing a progressive decline and deterioration. In the last decades, a series of seismic events caused considerable casualties and irreversible damage to historic centres in Italy, with permanent loss of many severely damaged cultural assets that could not be fully recovered or replaced. This problem underlines the need of undertaking further proactive measures to limit the impact of any potential earthquake on urban cultural heritage in historic centres. The characterisation of vulnerability in its multiple dimensions is a key issue for the effective implementation of vulnerability reduction and mitigation actions. This paper contests the enacting of seismic risk reduction programmes that are mainly based on the estimation of physical vulnerabilities and do not account for non-physical ones. The discussion is based on the Pressure and Release model that represents the progression of vulnerability in terms of unsafe conditions, dynamic pressures and root causes. The study refers to the historic centres in the Region of Tuscany (Italy) and considers a wider perspective on physical, socio-economic and institutional vulnerabilities. The results allows for outlining the agenda for action for risk reduction and establishing a set of mitigation strategies on the basis of the expected impacts of seismic events on historic centres. Intervention measures are integrated into the current framework for disaster risk reduction and aim to overcome the building-focused approach towards a large-scale systematic one.

Identifying Potential Earthquake Sources in Continental Environments

Identifying Potential Earthquake Sources in Continental Environments

Ambient noise tomography of local shallow structure of the southern segment of Tanlu fault zone at Suqian, eastern China

Comparable to San Andreas fault in western United States, the Tanlu fault zone (TLFZ) is a large-scale continental tectonic belt in eastern China and has played an important role controlling the regional tectonics and earthquake activity in eastern China. It is known there exists an earthquake gap in the southern segment around Suqian, Jiangsu province, where no earthquakes greater than M5.5 occurred. Fine fault zone structure could help to understand the fault activity and the potential earthquake hazards. However, only regional scale velocity model is available in this region, making it difficult to characterize detailed fault structures. In this study, we obtained local Vs model in the upper crust in this region by ambient noise tomography with a dense seismic array. For the Suqian segment, Cretaceous brittle normal faulting controlled the development of the eastern and western graben as well as the central horst between them. The graben-boundary faults are known simply as F1-F4 from east to west, and the NNE-striking fault F5 is between F1 and F2. The eastern boundary fault F1 and western boundary fault F4 separated by about 30 km are associated with intermittent high velocity anomalies in the shallow crust and are inactive. In comparison, faults F2, F5 and F3 are mainly associated with low velocity anomalies and are relatively active. These high velocity anomalies are very likely caused by the upwelling magma migrated along faults F1 and F4 in the crust, which on freezing could weld the fault zone and make it less active. Because faults F1 and F4 are hindered to move, the deformation could be transferred to nearby faults F2, F3 and F5. Our study sheds light on what controls fault activities along the TLFZ by obtaining local velocity structure in the Suqian segment.

Earthquake potential in the peripheral zones of the Ordos Block based on contemporary GPS strain rates and seismicity

Historically, devastating major earthquakes have occurred frequently in the peripheral zones of the Ordos Block. Thus, identifying possible locations of future catastrophic earthquakes in these regions is urgent both in the scientific community and in the public. For this purpose, we at first compute strain rates by means of GPS vectors and b-value from seismicity, then obtain geodetic earthquake potential. The calculation results show that high strain rates are mainly distributed in the peripheral zones of the Ordos Block with very small deformation in the interior of the Block, in good agreement with geology and seismicity. Based on seismic potential, considering historical and modern seismicity, and neotectonic structures together, we conclude that the west end of the Weihe Graben, southwest corner of the Ordos, is the most likely earthquake-prone area in future. Secondary risk regions for future strong earthquakes are located on the intersection between the Haiyuan fault and Liupanshan fault in the eastern Tibet, in the Yinchuan Graben and southwest of Hohhot around the Ordos Block. Therefore, this work may be significant for predicting earthquake risk and assessment of seismic hazard.

Performance of geophysical methods in determining fault zone at Darakeh Area (Tehran Province; Iran)

Darakeh area is one of the major areas in terms of seismic hazards in Tehran. The North Tehran Fault has gone through the center of the studied area, thus creating fractures, displacements and folds of layers, forming anticlines and synclines. Considering the old residential texture understanding the tectonic characteristics and locating the hidden faults of the region can be quite useful in providing thematic maps and preventing damages caused by potential earthquakes. Nevertheless, no geophysical studies have been carried out on this area so far. To map the area, three GPR and two electric resistivity profiles were designed based on the identified tectonic lineations and previous seismic studies on the area. Each GPR profile, was 100 m in length and surveyed using a MALA GPR with an unshielded 50-MHz antenna. The geo-electric profiles were surveyed by Wenner-Schlumberger array. The results of the processed profiles demonstrate a severe drop in resistivity in some regions which could be due to the presence of fault zones and potential cavities in the region under study.

Rapid Earthquake Loss Estimation Model for Algerian Urban Heritage: Case of Blida City

ABSTRACT The present work develops an integrated rapid loss assessment model aiming to quickly estimate the expected damages and their spatial distribution for the Algerian urban heritage context. It predicts the expected damages for a given earthquake scenario, i.e. an historic event or a reference scenario. Furthermore, in the immediate aftermath of an earthquake, the model updates the damages according to the seismic signals either recorded in the zone of interest or derived quickly from the GMPE (Ground Motion Prediction Equations). It combines a seismic damage assessment approach developed for existing building in Algeria and a GIS system, in order to automatically generate relevant damage maps for decision-making and rescue purposes. It is implemented and run for a real case of Blida city, located in the central northern part of Algeria, which is a highly dense urban area (3070 inhabitants/km2) containing an important architectural and historical heritage. For calibration purposes, the model is implemented and run in order to generate the seismic damage GIS maps for a set of 23,000 buildings, for a potential earthquake Mw = 7, consistent with the area seismicity. The results show that serious damages and complete destruction are expected in particular areas, mainly the oldest districts with an urban heritage consisting of old unreinforced masonry buildings dating from the XVI to the middle of the XX centuries. Less important damages are expected for newly erected constructions built during and after the last half of the XX century, as they meet the structural design standards and built on adequate soils.

Shallow crustal velocity structures revealed by active source tomography and fault activities of the Mianning-Xichang segment of the Anninghe fault zone, SW China

The Anninghe fault is a large left-lateral strike-slip fault in southwestern China. It has controlled deposition and magmatic activities since the Proterozoic, and seismic activity occurs frequently. The Mianning−Xichang segment of the Anninghe fault is a seismic gap that has been locked by high stress. Many studies suggest that this segment has great potential for large earthquakes (magnitude &gt;7). We obtained three vertical velocity profiles of the Anninghe fault (between Mianning and Xichang) based on the inversion of P-wave first arrival times. The travel time data were picked from seismograms generated by methane gaseous sources and recorded by three linearly distributed across-fault dense arrays. The inversion results show that the P-wave velocity structures at depths of 0−2 km corresponds well with the local lithology. The Quaternary sediments have low seismic velocities, whereas the igneous rocks, metamorphic rocks, and bedrock have high seismic velocities. We then further discuss the fault activities of the two fault branches of the Anninghe fault in the study region based on small earthquakes (magnitudes between <inline-formula><tex-math id="M1">\begin{document}$ {M}_{L} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA282-shaoxihui_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA282-shaoxihui_M1.png"/></alternatives></inline-formula> 0.5 and <inline-formula><tex-math id="M3">\begin{document}$ {M}_{L} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA282-shaoxihui_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="RA282-shaoxihui_M3.png"/></alternatives></inline-formula> 2.5) detected by the Xichang array. The eastern fault branch is more active than the western branch and that the fault activities in the eastern branch are different in the northern and southern segments at the border of 28°21′N. The high-resolution models obtained are essential for future earthquake rupture simulations and hazard assessments of the Anninghe fault zone. Future studies of velocity models at greater depths may further explain the complex fault activities in the study region.

Raised Potential Earthquake and Tsunami Hazards at the North Sulawesi Subduction Zone after a Flurry of Major Seismicity

Raised Potential Earthquake and Tsunami Hazards at the North Sulawesi Subduction Zone after a Flurry of Major Seismicity

Analisis Potensi Likuifaksi Berdasarkan Distribusi Ukuran Butir Tanah dan Data Cone Penetration Test (CPT)

Liquefaction is a failure phenomenon in the soil layer which generally occurs due to cyclic loads from earthquakes. This study was conducted to determine the potential for liquefaction based on soil grain size distribution and CPT data in the UII Hospital area in Wijirejo Village, Bantul, DIY. Based on its geographical location, the Bantul district has a high earthquake potential because it is near an opak fault and is located in a subduction zone between the Indo-Australian Plate and the Eurasian plate. Along with this, there is urgency for this research. Analysis based on the grain size distribution of the soil was evaluated using the Tsuchida curve (1970). Analysis based on CPT data was evaluated using the Seed &amp; Idris (1971) and IM Idriss &amp; RW Boulanger (2008) equations to obtain a soil layer safety value, which was then used to predict the level of potential liquefaction with the LPI value using the Luna &amp; Frost (1998) equation. Based on the grain size distribution using the Tsuchida curve (1970) in Wijirejo Village, the soil layer at a depth of 1 meter is dominated by sandy soil and silt, which has liquefaction potential. Based on CPT data, all sondir points have a very high liquefaction potential with consecutive LPI values 48,405; 52,160; 57,498; and 46,942 with a potential liquefaction zone depth of 0.20 to 13.20 meters from the ground level.

Transtensional Rupture within a Diffuse Plate Boundary Zone during the 2020 Mw 6.4 Puerto Rico Earthquake

Abstract On 7 January 2020, an Mw 6.4 earthquake occurred in the northeastern Caribbean, a few kilometers offshore of the island of Puerto Rico. It was the mainshock of a complex seismic sequence, characterized by a large number of energetic earthquakes illuminating an east–west elongated area along the southwestern coast of Puerto Rico. Deformation fields constrained by Interferometric Synthetic Aperture Radar and Global Navigation Satellite System data indicate that the coseismic movements affected only the western part of the island. To assess the mainshock’s source fault parameters, we combined the geodetically derived coseismic deformation with teleseismic waveforms using Bayesian inference. The results indicate a roughly east–west oriented fault, dipping northward and accommodating ∼1.4 m of transtensional motion. Besides, the determined location and orientation parameters suggest an offshore continuation of the recently mapped North Boquerón Bay–Punta Montalva fault in southwest Puerto Rico. This highlights the existence of unmapped faults with moderate-to-large earthquake potential within the Puerto Rico region.

Potential Study of Liquefaction in the Downstream Area of Jono Oge-Paneki River, Central Sulawesi

Liquefaction during an earthquake is likely to occur in the quaternary geological layer of sediment. Based on the geological process, the mainland of Central Sulawesi was initially a sea lifted upward to become land Palu-Koro fault. Therefore, the land is basically of basic alluvium soil formation, sand deposits, and loose rock. The earthquake in Central Sulawesi in September 2018 was the cause of liquefaction, one of which was in the Jono Oge area, where most of the flow entered the Paneki river. This paper analyzed the potential for recurrent liquefaction by considering the soil structure and water level conditions. The authors focused on the downstream areas of the Paneki River, which passes through Langaleso and Kabobona Village. The data used is N-SPT data, followed by examining post-liquefaction settlement and lateral displacement. This study uses several variations of the earthquake magnitude and potential earthquakes that may occur. The results of observations indicate that the soil conditions of the study area are cohesionless soil. The liquefaction analysis shows that most of the research areas have liquefaction, land subsidence, and lateral displacement potential.

Study of Liquefaction Potential at Sabo dam Construction on Poi and Bangga River, Sigi Regency, Central Sulawesi

The Palukoro fault, an active sinistral fault that cuts through Sulawesi Island, was the cause of the earthquake and liquefaction disaster in Palu and Sigi Regency in 2018. A series of studies related to liquefaction have been carried out since then but more focused on the west side of the Palu River. This research will raise the potential for liquefaction on the eastern side of the Palu river, precisely in the sabo dam area at Poi and Bangga River. These rivers are located on the opposite side of the Sibalaya liquefaction area. Liquefaction potential was calculated using the Simplified Procedure Method based on NSPT values. Fifteen and twelve boreholes are located at Bangga and Poi rivers, respectively. The qualitative analysis assessed the criteria of vulnerability based on geological factors, groundwater levels, and seismicity. The Liquefaction Potential Index method was used and calculated using several earthquake scenarios based on historical data and potential earthquakes of The Palu-koro fault. Based on LPI analysis, the Poi River has meager potential at the middle stream area and moderate level potential at the downstream. Bangga River has moderate to high liquefaction potential downstream and low to very low potential at the middle stream.

Arriving at estimates of a rate and state fault friction model parameter using Bayesian inference and Markov chain Monte Carlo

The critical slip distance in rate and state model for fault friction in the study of potential earthquakes can vary wildly from micrometers to few me-ters depending on the length scale of the critically stressed fault. This makes it incredibly important to construct an inversion framework that provides good estimates of the critical slip distance purely based on the observed ac-celeration at the seismogram. To eventually construct a framework that takes noisy seismogram acceleration data as input and spits out robust estimates of critical slip distance as the output, we first present the performance of the framework for synthetic data. The framework is based on Bayesian inference and Markov chain Monte Carlo methods. The synthetic data is generated by adding noise to the acceleration output of spring-slider-damper idealization of the rate and state model as the forward model.

KAPASITAS PANEL RUMAH INSTAN SEHAT BAJA RINGAN (RISBARI)

Indonesia has a very high earthquake potential. Disaster risk reduction requires the construction of earthquake-resistant housing. Rumah Instan Sehat Baja Ringan (RISBARI) is one of the proposals. There was no research on RISBARI building for the structural cyclic analysis, so it is necessary to assess the capacity of the structure. Cyclic experiment testing at panel RISBARI is required to find out the capacity and structural damage behavior. The experimental test was compared with the analytical analysis. Tests were on strap braced systems and shear wall systems panels. The peak capacity of the strap braced system panel on experimental testing is 2.75 kN and 2.94 kN under the analytical capacity of 7,314 kN. The panel collapsed at a drift of 2.46% (73 mm), under the drift limit of 5.5% (165 mm). The peak capacity of the shear wall panel on experimental testing is 8.77 kN and 8.16 kN under the analytical capacity of 13,354 kN. The panels collapsed at a drift of 3.4% (103 mm) is greater than the drift limit of 3% (90 mm). Damage type tearing of flanges and web determines panel capacity than other types of damage. The capacity of the panel immediately drops after the damage occurs.

Analysis of Tsunami Wave Height, Run-up, and Inundation in The Coastal of Blitar and Malang Regency

Indonesia is an archipelago located at the meeting point of 3 tectonic plates which constantly collide over time, the energy due to the collision will accumulate and be able to cause large earthquakes that can generate tsunamis. The island of Java is in the subduction zone of these plates, which causes the southern part of Java to have a high earthquake potential. On April 10, 2021, an earthquake measuring M 6.1 occurred in the south of Blitar and Malang. This earthquake was felt by most of the people of East Java, If the earthquake is large enough, it can cause a tsunami on the southern coast of East Java. Therefore, modeling was carried out using the FLOW module of Delft3D software while using earthquake parameters with a strength of M 9.1 which is the worst possible scenario on the southern coast of East Java. The results of this study indicate the fastest tsunami arrival time is 21 minutes, the highest maximum tsunami height is 20 meters, the highest run-up reaches 17,5 meters, and the furthest inundation reaches 765 meters along the southern coast of Blitar and Malang Regency.

Seismic resilient three-stage enhancement for gas distribution network using computational optimization algorithms

A computer-simulation-based three-stage optimization strategy is proposed for the resilience enhancement of urban gas distribution networks (GDNs). In stage I (pre-earthquake stage), the Fixed Proportion and Direct Comparison Genetic Algorithm (FPDC-GA) is applied to select key pipelines need to be strenthened or replaced under limited funding in preparation for future potential earthquakes. In stage II (post-earthquake stage), pressure tests must be carried out according to the gas leakage situation reported by users or detected by devices. The Multi-Label K-Nearest-Neighbor (ML-KNN) algorithm is used to predict the corresponding failed pipelines and optimize the pipeline pressure test order. In stage III (repair stage), a strategy based on a greedy algorithm is applied to optimize the pipeline repair sequence. The proposed methods were applied to the GDN of a city in northern China. The following conclusions were drawn from the results: (1) The FPDC-GA enhanced the robustness and resourcefulness of the GDN system to the maximum level within the available funding budget. (2) The pipeline pressure test order calculated using the ML-KNN algorithm was significantly improved compared with a random pressure test order or one based on the empirical failure probability of pipelines. (3) After optimization using a greedy algorithm, the performance recovery curves under different earthquake conditions were shaped as an exponential function, which indicates that the performance of the GDNs recovered in the most efficient manner. The findings of this study could be useful as tools for the seismic resilience enhancement of GDNs in different stages. The proposed optimization algorithms can also be extended to the lifeline of other networks.