Large Earthquake Events Research Articles

Can we quickly retrieve Seismic Source Spectrum characteristics after a large magnitude earthquake? Implementation of a methodology based on Coda waves

After a large magnitude earthquake event, the direct estimation of its Seismic Source Spectrum (SSS) is important to estimate the energy content of the seismic source in broad-band frequency range. This direct knowledge of the SSS, except for the fact that can directly provide information about the Moment Magnitude of the earthquake, constitutes also, in frequency domain, that information, which is required to the Fourier Amplitude Spectra (FAS) simulation of the real-input seismic motion, in several target sites close to the source for which no earthquake recordings exist. In this study, the computation of the SSS of an earthquake is based on a single-station analysis algorithm by applying the spectral factorization method on the coda wave part of a seismic record. An application of this algorithm is implemented here for the Mw = 6.1 Cephalonia Island earthquake of 26/01/2014. The corresponding SSS, computed for several stations away from the source, are compared with the average SSS retrieved by standard applied method. The comparison results strongly encourage application and development of this SSS computation approach.

Probabilistic seismic hazard function based on spatiotemporal earthquake likelihood simulation and Akaike information criterion: The PSHF study around off the west coast of Sumatra Island before large earthquake events

The probabilistic seismic hazard function (PSHF) before large earthquake events based on the hypothesis earthquake forecast algorithm using the Akaike information criterion (AIC) is performed in this study. The motivation for using the AIC is to better understand the reliability model used to construct the PSHF. The PSHF as the function of the b-value is calculated based on a 5-year window length with a 1-year moving window (instantaneous PSHF) before a large earthquake event. The AIC is calculated based on the likelihood of success and failure using shallow earthquake catalog data around the west coast of Sumatra Island. The probability of occurrence defines the success criteria as more significant than the average probability of greater than or equal to the given magnitude; otherwise, it is defined as failure. Seismic potency has been determined based on the likelihood of an earthquake occurring in several decades or a hundred years. The seismicity rate model is developed based on the integrated data of pre-seismic shallow crustal movement data and the shallow crustal earthquake catalog data. Furthermore, the AIC is calculated based on the likelihood of success and failure as a function of b(t). The b(t) is the change in the b-value as a time function estimated based on shallow earthquake data from 1963 to 2016. In addition, the AIC before M7.9 of 2000, M8.5 of 2007, and M7.8 of 2010 is assessed. The δAIC is then introduced as a function of (AICmodel–AICreference) during the observation time. The positive δAIC implies that the likelihood of having a large earthquake is more significant; otherwise, it is smaller. By plotting the time of observation versus δAIC and the PSHF estimated as the function of b(t), we could identify a large positive gradient and increase the PSHF at each certain probability exceedance (PE) level before the great earthquake event. It consistently happened for the three events that were evaluated. It suggested that the results of this study might be very beneficial for probabilistic seismic hazard analysis (PSHA) and seismic mitigation realization.

Probabilistic earthquake hazard parameterization for Indo-Burma region using extreme value approach

The Indo-Burma area is one of the most seismically active regions because of subduction of the Indian plate under the Burmese plate. The Indo-Burma area, which is bordered by 22°–27°N and 92°–97°E, has of late witnessed multiple moderate-to-large earthquakes. Seismic hazard assessment has been performed using the well-known extreme value theory, including estimate of return periods and likelihood of occurrence of medium to large earthquake events. The Indo-Burma region's seismic hazard parameterization has been computed using a homogeneous and thorough earthquake database created for the time span between 1973 and 2021. Due to an insufficient dataset, the b-value calculated using the GR relation was determined to be unsatisfactory (0.58). Therefore, the b-value was estimated using Gumbel's extreme value approach (0.902). The findings show that earthquake of 5.352 magnitude is likely to be the greatest annual earthquake in the study area. Additionally, the most likely large earthquakes that might happen throughout a wide range of periods have been projected and displayed.

The refinement of reprocessed GNSS three-decade displacement trajectory model with spectral analysis and hypothesis test

Extensive data collection, unified and rigorous data processing, and accurate construction of station motion model (especially the correction of co-seismic/post-seismic effects of large earthquakes) are three basic elements for the accuracy and reliability of Global Navigation Satellite System (GNSS) velocity. Thus, we take advantage of the sensitivity features of the spectral analysis and hypothesis test to refine the site movement trajectory model, and apply it to the reprocessed GNSS three-decade coordinate time series. Firstly, we reprocess GNSS observations and seismic records based on the updated convention and processing settings of International GNSS Service (IGS) repro3. Secondly, we use the Improved Lomb–Scargle Periodogram (ILSP) model to analyze the periodic characteristics of GNSS vertical time series. The results represent that the primary period of about 35% of sites is 365 days, and the secondary period of 20% of sites is 182 days. Thirdly, we evaluate the performance of different time series model component combination of the time series (a: velocity only; b: velocity + offset; c: velocity + offset + PSD; d: velocity + offset + PSD + period) and Post-Seismic Deformation (PSD) modes (PSD1: None; PSD 2: Exp; PSD 3: Log; PSD 4: Exp + Log). Fourthly, we use the chi-square test to assess the overall correctness of the trajectory model, followed by the t-test to test the significance of each parameter further, and then use the optimized model to refit and reanalyze GNSS time series. The analysis of the velocity results illustrates that the fitting accuracy of GNSS time series is 3–6 mm in the horizontal direction and 4–9 mm in the vertical direction. Lastly, we obtain a refined global three-dimensional velocity field based on GNSS three-decade time series, with the median velocity of Root Mean Square Error (RMSE) as 0.17, 0.17, and 0.32 mm/a in N/E/U direction. Compared with ITRF2014, the velocity difference is at 1–2 mm/a level due to differences in GNSS observations, trajectory model, and geodetic technology.

Recurrence and Clustering of Large Earthquakes along the Northern Boundary of Ordos Block: Constraining Paleoearthquakes by an Improved Multiple Trench Constraining Method

AbstractTectonic belts along active tectonic block boundaries comprise one or more active faults; along which, large earthquakes recur. Therefore, it is important to establish the recurrence behavior of large earthquakes along such boundary zones for studying their characteristics and developments. Many paleoearthquake studies make it possible to investigate the recurrence behavior of large earthquakes along the northern boundary of the Ordos block (NBOB). Based on the previous studies, data from 52 trenches were collected to reconstruct prehistoric earthquakes using an improved multiple trench constraining method. This method is based on paleoearthquake indicators and trench location distribution to constrain the rupture time and length, thereby reducing the selection bias of fixed rupture length to construct additional rupture scenarios. The results suggest that the NBOB comprises four normal faults (from west to east): the Langshan Piedmont Fault (LPF), Sertengshan Piedmont Fault (SPF), Wulashan Piedmont Fault (WPF), and Daqingshan Piedmont Fault (DPF); along which, six, seven, eight, and six paleoearthquakes have occurred within approximately 15,000 yr, respectively. In addition, recurrence behaviors of the individual faults exhibit remarkable periodicity. The regional fault network along the NBOB reveals clustered characteristics with six clusters propagating either westward or eastward and a recurrence time of approximately 1,300 yr. Large earthquake events have occurred along the LPF, WPF, and DPF according to the most recent cluster; however, earthquakes were absent along the SPF, and no evidence of large earthquakes was observed along the NBOB after the 849 CE earthquake. Thus, we discuss the possibility of occurrence of large earthquakes along the SPF after the 849 CE earthquake based on earthquake recurrence and cluster migration behavior. Additional research is required to assess the potential risk of the occurrence of a large earthquake along the SPF in the future.

The Effect of the Wenchuan and Lushan Earthquakes on the Size Distribution of Earthquakes along the Longmenshan Fault

Changes in the stress state of faults and their surroundings is a highly plausible mechanism explaining earthquake interaction. These stress changes can impact the seismicity rate and the size distribution of earthquakes. However, the effect of large earthquakes on the earthquake size distribution along the Longmenshan fault has not been quantified. We evaluated the levels of the b value for the stable state before and after the large earthquakes on 12 May 2008 (Wenchuan, MS 8.0) and 20 April 2013 (Lushan, MS 7.0) along the Longmenshan fault. We found that after the mainshocks, the size distribution of the subsequent earthquakes shifted toward relatively larger events in the Wenchuan aftershock zone (b value decreased from 1.21 to 0.84), and generally remained invariable in the Lushan aftershock zone (b value remained at 0.76). The time required for the b value to return to stable states after both mainshocks was entirely consistent with the time needed by the aftershock depth images to stop visibly changing. The result of the temporal variation of b values shows decreasing trends for the b value before both large earthquakes. Our results are available for assessing the potential seismic risk of the Longmenshan fault as a reference.

Seismic vulnerability assessment of ageing reinforced concrete structures under real mainshock-aftershock ground motions

Ageing structures located in moderate to high seismicity regions are exposed to multiple natural stressors during their lifetime. Large earthquake events coupled with environmental aggressive agents increase the progressive failure probability of these structures. The accumulated damage during the main earthquake event might be exacerbated by its following aftershocks. This might result in catastrophic failure of these structures, and consequently, result in several socio-economic losses. Taking such progressive deterioration mechanism into consideration, the current study presents a framework to assess the vulnerability of ageing Reinforced Concrete (RC) frames subject to real Mainshock-Aftershock (MS-AS) ground motion sequences. Employing an advanced fibre-based finite element modelling technique, the nonlinear static and dynamic behaviour of a case-study RC frame with various ages is simulated under 48 real MS-AS record pairs. Quantifying corrosion-variant damage states, the age-specific fragility curves are developed for the considered structure under both single MS events and MS-AS sequences. It was found that the severely corroded RC frames are most likely to collapse before the second event comes up. Moreover, results show that the PGA ratio of AS to MS plays a critical role in seismic vulnerability assessment of highly corrosion-damaged RC frames.

Effect of Long-Distance Earthquake from Philippines and Sulawesi to Sabah Region

Sabah is known for its active earthquake activities, especially in Ranau, Kudat and Lahad Datu areas. The effects of local earthquake can reach M W 6.0. Furthermore, Sabah was also hit by earthquakes from neighbouring countries such as Sulawesi and Philippines. These countries produce highly active earthquakes that can reach as high as M W 8.6. The increase in the frequency of earthquakes is one of the concerns of the Sabah government for the safety of its people because most people live in concentrated areas near the coast. This study shows the effects of major earthquakes from the Philippines and Sulawesi which have been recorded between 1900 to 2020 and analyzed in terms of peak ground acceleration (PGA). The eastern region of Sabah is adopted in the analysis for the effect of long-distance earthquakes, as these areas are close to both countries. The analysis uses standard seismic hazard assessment procedure with compilation magnitudes greater than M W 5.0. In the final analysis, it is shown that the effects of large earthquakes from both countries are relatively small compared to the effects of local earthquakes.

Design optimization of triple friction pendulums for high-rise buildings considering both seismic and wind loads

Triple friction pendulum isolation bearings are typically designed with only earthquakes in mind, or perhaps with a large enough initial friction coefficient to limit displacement under wind loads. However, for potential application in high-rise buildings, wind demand is of greater concern, and the increased flexibility of the structure can lead to wind-induced floor accelerations that exceed the serviceability limit state. To determine the optimum parameters of triple friction pendulum bearings that minimize the structural response under both wind and seismic loading in high-rise buildings, an optimization methodology (fast elitist non-dominated sorting genetic algorithm) is used. Cost functions are proposed that penalize the story drift and floor acceleration under wind and all earthquake hazard level as well as isolation displacement under large earthquake events. First, a genetic algorithm (GA) is adopted to find the optimal parameters of the bearings designed separately for wind and earthquake excitations. However, the triple friction pendulum bearing (TFPB) designed optimally for earthquake excitation provides less than optimal wind-resistant performance and vice-versa. Afterwards, a multi-objective optimization is used which allows for a tradeoff between the seismic isolation and wind-resistant performance. The design parameters of TFPB can then be selected to achieve the best seismic isolation performance while ensuring that the performance under wind-loading meets requirements.

Composite Multiscale Cross-Sample Entropy Analysis for Long-Term Structural Health Monitoring of Residential Buildings.

This study proposesd a novel, entropy-based structural health monitoring (SHM) system for measuring microvibration signals generated by actual buildings. A structural health diagnosis interface was established for demonstration purposes. To enhance the reliability and accuracy of entropy evaluation at various scales, composite multiscale cross-sample entropy (CMSCE) was adopted to increase the number of coarse-grained time series. The degree of similarity and asynchrony between ambient vibration signals measured on adjacent floors was used as an in-dicator for structural health assessment. A residential building that has been monitored since 1994 was selected for long-term monitoring. The accumulated database, including both the earthquake and ambient vibrations in each seismic event, provided the possibility to evaluate the practicability of the CMSCE-based method. Entropy curves obtained for each of the years, as well as the stable trend of the corresponding damage index (DI) graphs, demonstrated the relia-bility of the proposed SHM system. Moreover, two large earthquake events that occurred near the monitoring site were analyzed. The results revealed that the entropy values may have been slightly increased after the earthquakes. Positive DI values were obtained for higher floors, which could provide an early warning of structural instability. The proposed SHM system is highly stable and practical.

Damping Estimation of an Eight-Story Steel Building Equipped with Oil Dampers

The damping estimation of an eight-story steel building equipped with oil dampers is examined, carried out by adopting a proposed framework, which consists of an enhanced strain-energy method and an improved direct method for model updating. The building is located at Tohoku Institute of Technology and is equipped with a structural monitoring system that measures its seismic response, including floor acceleration and displacement and force of oil dampers. The enhanced strain-energy method is first developed and employed to assess the supplemental damping and stiffness provided by oil dampers, herein quantified in the form of equivalent damping ratios and natural frequencies. Then, modal characteristics extracted from the earthquake measurements are modified accordingly and utilized for the building model updating, in which mass and stiffness matrices are corrected by the improved direct method. The updated model accurately reproduces the target modal data, especially measured mode participation factors, and is further used for the building response predictions. Through prediction validations, the precision of the modified modal parameters is verified. Finally, a large earthquake event is chosen to demonstrate the effectiveness of the proposed framework for the damping estimation of the investigated building.

Case studies on suction caisson foundations in offshore wind farms in China

ABSTRACT Suction caissons are cylindrical-shaped foundation elements closed at the top and open at the bottom which are almost completely embedded with their cylindrical part in the soil. The main advantage of this foundation compared to other commonly used foundation concepts is its fast, ease, and almost noiseless installation, as well as the effortless removal at the end of the lifetime. Suction caissons supporting three- or four-legged jackets have been employed successfully in several recent offshore windfarm projects around the world. The study presented herein investigates the general suitability of suction caissons in the south china sea at three representative sites. The results show that suction caisson foundations are technically feasible. Sizes can be large and may vary between 13 m to 15 m in diameter and 10 m to 13 m in length, which, however, may reduce noticeably when considering load redistribution in the design, typically done in a FEED and detailed design. The main challenges of suction caisson application are the very soft soil conditions and possible liquefaction potential due to large earthquake events. Although technically feasible, the economic viability of suction caissons needs to be investigated on project-specific basis. For that purpose, the authors provide an overview of general aspects which need to be considered in such an evaluation. This study gives realistic case studies for research and industry in offshore wind farm development.

Seismic study and spatial observations of a & b – values for the different earthquake hazard zones of India

This paper study the recent seismicity in Earthquake hazard zones in India. A large historical earthquake event catalog to cover the period of 1900-2018, the parameters date, time, latitude, longitude, depth and magnitude has been used to calculating frequency-magnitude distribution (b-value) of seismic hazard zones in India. To convert different magnitude scales into a single moment magnitude scale, the general orthogonal regression relation is used. Gamma distribution used for variable corrections also de-clustering method has used for removal of any non-Poisson distribution. The Indian seismic hazard zones are divided into five major seismic sources zones. The seismicity is characterized by Gutenberg-Richter relation. The parameter ‘b’ of FMD and relationship have been determined for these five seismic zones having different vulnerability environment. The ‘b’ values ranges between 0.43 to 1.16. The difference between the b parameters and seismic hazard level from seismic zones II to V considered for the study of high seismo-tectonic complexity and crustal heterogeneity, the parameter ‘a’ value changes accordingly the seismicity of the regions. The lowest b-values found in seismic zone II. The highest FMD b-value has been found in the seismic zone IV. Such high seismicity b-values may be associated with high heterogeneity. In this high b-value predict the low strength in the crust as well as seismic instabilities of that zone. These observations recommend not suggesting the location of important projects like atomic power stations, hydroelectric power stations, neutrino observatory projects, satellite town projects.

Factors That Affect Liquefaction-Induced Lateral Spreading in Large Subduction Earthquakes

Liquefaction-induced lateral spreading can induce significant deformations and damage in existing structures, such as ports, bridges, and pipes. Past earthquakes have caused this phenomenon in coastal areas and rivers in many parts of the world. Current lateral spreading prediction models tend to either overestimate or underestimate the actual displacements by a factor of two or more when applied to large subduction earthquake events. The purpose of this study was to identify ground motion intensity measures and soil parameters that better correlate with observed lateral spreading under large-magnitude (Mw ≥ 7.5) subduction earthquakes that have occurred in countries like Chile, Japan, and Peru. A numerical approach was first validated against centrifuge and historical cases and then used to generate parametric models on which statistical analysis was applied. Our results show that cumulative absolute velocity (CAV), Housner intensity (HI), and sustained maximum velocity (SMV) have a reasonably good correlation with lateral spreading for the analyzed cases.

CRUSTAL DISPLACEMENT BASED ON THREE STAGES GEODETIC STUDIES RESULTS IN SPITAK GEODYNAMIC POLYGON

A network of dual-frequency global navigation satellite systems and digital levelling instruments has been established around Spitak, Armenia with the goal of recording changes to the Earth’s crust near to this major earthquake zone. The study was initiated in response to the 1988 Armenian earthquake and is focused on the Sarighamish, Javakhet, Pambak-Sevan, Spitak and Akhuryan faults. Results demonstrate differential movement across fault zones that suggest monitoring of crustal change could be useful in the predicition of large earthquake events.

New insights into Holocene marine terrace development caused by seismic and aseismic faulting in the Coastal Range, eastern Taiwan

The Coastal Range in eastern Taiwan, which has resulted from arc-continent collisions, involves well-developed Holocene uplifted marine terraces along a 140-km long stretch of the coast. This is the first study that unraveled the aseismic generation of marine terraces associated with coseismic uplift along the creeping fault. We organized DEMs/LiDAR mapping and field surveys to obtain detailed and systematic measurements of the inner and outer edges and wave-cut platform elevations along thirty-three stream profile transects, allowing us to locate the bedrock profile. Spatial and temporal variations in the 14C age are characterized by an offlapping built feature of significant seaward younging trend of ages across the marine terrace, caused by aseismic and coseismic uplift. Thus, heights of the bedrock riser and platform are caused by coseismic (large earthquake) and aseismic plus moderate coseismic vertical deformations during a large earthquake cycle, respectively. This indicates that each terrace duration and paleoshoreline ages can be used to infer the recurrence interval and the timing of large earthquake events, respectively. Results of the age of the paleoshoreline indicate six paleoseismic events at ∼8500, ∼6300, ∼4800, ∼3400, ∼1700, and ∼700 yr BP. This implies that the Chihshang creeping Fault could be capable of producing large earthquakes (greater than M7) at millennial time scales associated with larger coseismic deformations. The creep faulting associated with seismic and aseismic uplift is a dominant process constraining the Holocene marine terrace evolution.

Tsunami evacuation simulation for the District of Tofino, Vancouver Island, Canada

A large earthquake event generated from the nearby Cascadia Subduction Zone would possibly generate a significant tsunami event which could affect the west coast of Canada. In this study, to critically assess the effects of a tsunami on the District of Tofino on Vancouver Island, British Columbia, tsunami simulations were performed. As a result of tsunami propagation and inundation simulations, it was found that for earthquakes Mw9.0 or greater, the central part of the Esowista Peninsula on which Tofino is located will be completely inundated. The authors have also conducted tsunami evacuation simulations using an agent-based model developed by Takabatake et al. (2017). This evacuation model considered Tofino's large fluctuation in residents due to seasonal tourism in a number of selected scenarios. Using the model, the authors also conducted a sensitivity analysis to investigate effects of the change in evacuation behaviour on the mortality rate. The results showed that a significant number of casualties would occur in Tofino, especially if an earthquake was to occur at night. It was also shown to be important to consider the capacity of evacuation buildings when directing evacuees, especially the elderly. In addition, the present study clarified that the effects of evacuation start time and route choices on the mortality rate would vary significantly according to a population distribution scenario even in the same study area. It was thus highlighted that conducting sensitivity analysis under varied population distribution scenarios is important to understand properly the uncertainty associated with tsunami evacuation.

Case Studies on the Practical Application of Resilient Building Technologies Applied in New Zealand

Seismic design of buildings in New Zealand follows the principles of ductility and capacity design, targeted at life safety as well as avoidance of building collapse in large earthquake events. The inevitable result of ductility is damage to the primary structure, which absorbs the seismic energy during an earthquake. In smaller, more frequent earthquake events, the New Zealand standards recommend limits to building drifts to avoid structural and non-structural damage to building elements. The Canterbury Earthquakes of 2010 and 2011 provided the impetus to construct buildings with more focus on resilience as it became clear that traditional forms of building construction do not always provide the best solution for easy repair and continued operation, with many buildings having to be demolished, causing widespread disruption. An increasing number of new buildings have been constructed in New Zealand utilising different forms of seismically resilient building technologies. This paper presents case studies demonstrating some of the techniques used to provide the building structures with more resilience. Resilient technologies used in the presented case studies include triple friction pendulum bearings, innovative dissipative steel plate connectors, sliding hinge joints, Ringfeder® hold-down springs, U-shaped flexural plates, post-tensioning, and compression- and tension-yielding plug-and-play dissipaters.

A probabilistic seismic hazard model for North Africa

African seismicity is predominantly localized along the East African Rift System (EARS), which is the major active tectonic feature of Sub-Saharan Africa. Besides the EARS, however, significant seismicity also occurs along a wide belt bounding the Mediterranean coastline. This tectonically active region extends discontinuously from Morocco to Egypt and its activity is controlled by the complex interaction between the Nubian and Eurasian plates, varying from transpression in the Atlas orogen in the west to transtension in the east. A record of large earthquake events is documented for the whole region, some of them causing moderate to severe levels of damage, mostly because of the high vulnerability of local buildings and structures, a condition which is still largely persistent in many areas. Currently, a number of seismic hazard models exist at local and national scales for North Africa, developed within independent projects and created using inhomogeneous data sources and different processing techniques. Unfortunately, such diversity makes their direct comparison problematic, obscuring the differences in seismic hazard across neighbouring areas and preventing the development of comprehensive long-term risk mitigation strategies. In fact, the last effort to produce a homogenized model for the whole Africa continent dates back to the GSHAP project, which is almost 20 years old. The creation of a unique seismic hazard model for North Africa, uniform across countries, is therefore a main concern. Since its inception, the Global Earthquake Model Foundation (GEM) is committed to the creation of a worldwide mosaic of high-quality, reproducible and openly accessible seismic hazard models, uniformly represented using the format adopted by the OpenQuake engine (OQ), a state-of-the-art, free and open-source software package for seismic hazard and risk assessment. We describe the development of a new comprehensive PSHA model for North Africa using GEM tools. The source model combines active faults and distributed seismicity, the former constrained from published geological descriptions and geodetic data, while the latter from the harmonisation of published earthquake catalogues.

Load-displacement Response of Gravity Load Designed Reinforced Concrete Moment Frames with Various Height of Masonry Infill Walls

Lightly reinforced concrete (RC) moment frames may suffer significant damage during large earthquake events. Most buildings with RC moment frames were designed without considering seismic loads. The load-displacement response of gravity load designed frames could be altered by masonry infill walls. The objective of this study is to investigate the load-displacement response of gravity load designed frames with masonry infill walls. For this purpose, three-story gravity load designed frames with masonry infill walls were considered. The masonry infilled RC frames demonstrated larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. A specimen with a partial-height infill wall showed the least drift capacity and energy dissipation capacity. This specimen failed in shear, whereas other specimens experienced a relatively ductile failure mode (flexure-shear failure).