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On September 18, 2022, an earthquake with a local magnitude (ML) 6.8 struck the southern part of Longitudinal Valley in southeastern Taiwan, resulting in the collapse and damage of many engineering structures. A field reconnaissance was conducted at the selected sites that experienced building and bridge damages and is presented in this paper. The focus is on geotechnical problems such as strong ground motion, ground rupture, soil liquefaction, and their influence on engineering structures. Strong motions of up to 0.6 g were induced, with similar intensity in the vertical and horizontal components near the epicenter. Widespread ground rupture traces were observed along the officially recognized active faults, inducing offsets up to tens of centimeters. Soil liquefaction was also noticed in this region, mainly on the river flood plain and characterized as gravel layer. The possible influence of these observed geotechnical characteristics on the damage pattern or failure mode of buildings, bridges, embankments, and levees was discussed and interpreted insightfully. The perspectives presented in this paper may serve as a reference to disaster prevention and mitigation in future events. [ABSTRACT FROM AUTHOR]

The devastating earthquake of 2015 in Nepal overwhelmed the Nepal government, which resulted in the government seeking help from the international community. The call from the Nepal government was responded to quickly by many countries. While the government accepted the help from far countries, the Nepal government rejected the humanitarian aid offered by Taiwan saying that Nepal only takes such aid from its neighboring countries. This paper examines the reasons behind the aid rejection of Taiwan by Nepal and tries to answer what could have happened if it was accepted. Though Nepal is one of the Least Developed countries, even during the disaster time, the aid was rejected. The paper concludes that, even during the most crucial time, there is politics in accepting aid. Nepal's rejection of Taiwan's aid was because of the pressure to obey the diplomatic relation with China, as Nepal is dependent on China but not on Taiwan. [ABSTRACT FROM AUTHOR]

The region around Taiwan is known for high seismicity. Under the circumstances, seismic hazard assessments and proper earthquake-resistant designs are essential to the region. From a well-studied earthquake catalog, this paper presents the statistics of major earthquakes (i.e., moment magnitude Mw = 5.5 and distance = 200 km) around the most important city in Taiwan (i.e., Taipei). The analysis shows that the mean annual rate of the major earthquakes is 2.79 around the city, with mean magnitude and SD equal to Mw 6.12 and 0.68, respectively, and mean source-to-site distance and SD equal to 129 and 39 km, respectively. With the earthquake statistics and local ground motion models, a seismic hazard assessment was conducted with Monte Carlo simulations (MCSs). The analysis shows the mean rate for peak ground acceleration = 0.23g (where g is gravitational acceleration) should be around 0.013 per year, indicating that the current design peak ground acceleration in Taipei. From this paper, the current seismic design in Taipei might not be as conservative as expected, and a review and revision could be needed for assuring the city's seismic safety against high seismicity in the region. [ABSTRACT FROM AUTHOR]

In this paper, we focused on the characteristics of the seismo-ionospheric effects related to two successive earthquakes, namely, the earthquakes in 2022 in Taitung Sea, Taiwan, China, with magnitudes (M) of 6.7 and 6.3, at 23.45° N, 121.55° E and 23.39° N, 121.52° E and with the same focal depth of 20 km, which were detected by the China Seismo-Electromagnetic Satellite (CSES). By applying the sliding interquartile range method to electron density (Ne) data acquired by the Langmuir probe (LAP) onboard the CSES and the grid total electron content (TEC) data obtained from the Center for Orbit Determination in Europe (CODE), positive anomalies were found under quiet geomagnetic conditions on 2–3 March and 8–9 March 2022—that is, 19–20 and 13–14 d before the earthquakes, respectively, and the global ionospheric mapping (GIM) TEC data suggested that anomalies may also have been triggered in the magnetic conjugate area 13–14 d prior to the earthquakes occurrences. In addition, the CSES Ne data showed enhancements 3 and 5 d before the earthquakes occurred. Furthermore, 138 earthquakes with M ≥ 5.0 that occurred in Taiwan and the surrounding region during the period February 2019 to March 2022 were statistically analyzed using the CSES Ne data. The results show that most of the Ne anomalies were positive. Moreover, the greater the earthquake magnitude, the greater the frequency of the anomalies; however, the amplitude of the anomalies did not increase with the earthquake magnitude. The anomalies were concentrated during the period of 10 d before to 5 d after the earthquakes. No increase in the amplitude of anomalies was observed as the time of the earthquakes approached. Finally, based on evidence relating to earthquake precursor anomalies, we conclude that it is possible that earthquakes in Taiwan and the surrounding region affect the ionosphere through the geochemical, acoustic, and electromagnetic channels, as described by the lithosphere–atmosphere–ionosphere coupling (LAIC) model, and that the two studied earthquakes in Taiwan may have induced ionospheric effects through the geochemical channel. [ABSTRACT FROM AUTHOR]

Purpose: In the current study, the researchers tracked the steps that were taken (in the past 20 years after the occurrence of the 921 earthquake) to enhance the safety of students and teachers on campus by rebuilding the schools according to higher standards. Additionally, the researchers analyzed the process of school reconstruction in Taiwan after the Chi-Chi earthquake, as well as the resilience of the rebuilt schools. Design/methodology/approach: This paper collected extensive relevant literature to serve as a basis for data analysis. Subsequently, they examined the conditions of selected schools before and after they were affected by the earthquake, as well as the reconstruction process of these schools. The purposive sampling method was also adopted to assemble a unique and representative sample. Findings: This study concluded a new disaster risk reduction education system in Taiwan, from safe learning facilities, school disaster management and risk reduction and resilience education perspectives. It encouraged school and community collaboration regarding establishing a comprehensive disaster management framework. Originality/value: The paper kept tracks of how schools recovered and restored after the 921 earthquake based on global disaster management trends and local disaster risk reduction education. It also highlighted the major changes within the school resilience system and the importance of disaster risk reduction education in Taiwan. [ABSTRACT FROM AUTHOR]

Monitoring precursory decline in groundwater radon at the Antung hot spring is a useful means of forecasting the magnitude and precursor time of local disastrous earthquakes. With the help of a case study in southeastern Taiwan, this paper demonstrates the effect of tectonic setting in the subduction zone on the correlation between radon decline, precursory time and earthquake magnitude. Given a radon-monitoring site located near the plate boundary in the tectonic setting of advanced arc-continental collision, the observed radon decline and precursory time prior to the earthquakes in the tectonic setting of initial arc-continental collision are smaller than those observed prior to the earthquakes occurring on the plate boundary in the tectonic setting of advanced arc-continental collision. In the advanced arc-continental collision state, the coupling between the plates is strong and the stress transfer is efficient, whereas in the incipient collision state, the coupling and stress transfer are not as good. It also takes additional time lag and attenuation for the stress transfer from one tectonic setting to the other. This paper presents the difference in the precursory behavior of groundwater radon between earthquakes which occurred in two different tectonic settings: advanced and initial arc-continental collision. [ABSTRACT FROM AUTHOR]

Earthquakes as a natural hazard have caused substantial economic losses and human life loss in many countries. Taiwan, which is located on the western Circum-Pacific seismic belt, encountered this problem in the form of the Meishan, Hsinchu-Taichung, and Chi-Chi earthquakes a few years ago. In this paper, the researchers propose a novel robot-event integrated system capable of doing the automated inspection and emergency response due to a significant earthquake. As the household's earthquake warning receiving device picks up an alert, its built-in wireless communications system will send a signal to the robot. The robot will then commence the inspection of the indoor area via real-time image recognition and tracking. Upon detecting fallen people, it will approach them, regulating their movements via the robot operating system monitoring interface. The robot is designed to operate in a house that remains standing with acceptable damage in which the furniture might be falling and injure the occupants after an earthquake hit. The indoor experiment was conducted to verify the robot system and operation with a designed condition such as fallen and non-fallen people as the detected object. The precision of the robot arm was tested in the case of the delivery of supplies to the fallen people while waiting for the rescuers to arrive. The tests indicated that the proposed smart robot has prospective implementation in real-world applications with more research and development. The smart robot integrated with an earthquake early warning system is a promising approach to the temporary care of people affected by earthquakes. [ABSTRACT FROM AUTHOR]

The paper presents the analysis of collapse and damage state to some special buildings during recent severe surface earthquakes, The presented irregular reinforced concrete buildings (with irregular distributions of mass, stiffness, strength, geometrical configurations), especially the setback structures and tall structures, have exhibited a poor seismic performance. Through graphical representations of response spectra obtained from records, it is revealed that most of the damage occurred to buildings due to exceeding the code requirements, the level of accelerations and to the spectral composition, unusual to the surface earthquakes, which justify the shown interest. Comparative analysis of numerical data is shown in order to put into evidence the effects of surface earthquakes on buildings. It must be accepted that an important role in the overall behaviour of the presented buildings had the higher modes of vibration and shaking time, beyond the technical aspects. What is noticeable, also, are the long periods of motions, although the earthquakes are of surface. The more accelerograms recorded are, we find that the possible values may be higher than those from design codes and sometimes the codes provisions are taken from other design rules (with other local features). [ABSTRACT FROM AUTHOR]

Background: Few studies have explored the field experiences and risk factors related to post-traumatic stress disorder (PTSD) among disaster rescue workers., Methods: A 6.4-magnitude earthquake struck southern Taiwan on February 6, 2016. A standardized, paper-based, self-administered survey questionnaire including demographic information, field experiences and the Post-Traumatic Stress Disorder Checklist (PCL) was conducted among emergency medical technicians (EMTs) one month after the earthquake. A multivariate regression model was used to analyze the associations between risk factors and the PCL. A two-sided p value less than 0.05 was considered statistically significant., Results: The survey response rate was 86.1% (447/519). The respondents who exceeded the cut-off points for the re-experience, avoidance, or hyperarousal domains were 11.8%, 2.7%, or 4.7%, respectively. A proportion of 12.7% of respondents met partial PTSD. The personality characteristics of anxiety (p < 0.001), perfectionism (p = 0.023) and introvert tendency (p = 0.002) were significantly correlated with partial PTSD. Emergency medical services (EMS) were significantly associated with partial PTSD than other main tasks (p < 0.001). The prevalence of partial PTSD was higher but was not significantly different in the groups of lower educational level, longer EMT careers, earlier arrival date, fewer field working hours, or managing dead people. Both univariate and multivariate logistic regression analyses showed that an anxious personality and EMS as the main task during the missions were significantly associated with PTSD risk., Conclusion: Not only personality characteristics but also the task components could alter the PTSD risks in disasters. A broad realization of these risks may improve the mental outcomes of disaster rescuers., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to report. The authors are solely responsible for the content and writing of the paper., (Copyright © 2019 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.)

Although several factors associated with posttraumatic stress disorder (PTSD) in disaster rescue workers were identified in previous studies, the results were inconsistent. This study aimed to explore the prognostic factors of PTSD among disaster rescuers using different screening tools. A 6.4 magnitude earthquake struck southern Taiwan on February 6, 2016. Emergency medical technicians (EMTs) who responded to the earthquake were recruited. The initial survey was conducted one month after the earthquake using a standardized, self-reported, paper-based questionnaire. After six months, we re-evaluated the EMTs using the same questionnaire that was used in the baseline survey. A total of 38 EMT-paramedics were enrolled in the final analysis. Significant differences in PTSD scores at baseline existed between EMTs with and without certain risk factors. The interaction between survey time and risk factors was not significant, but several risk factors correlated with a nonsignificant improvement in the PTSD score after the 6-month follow-up. Perfectionism personality characteristics and several specific field experiences (managing injured patients, managing dead victims, managing dead victims who were pregnant, managing emotionally distraught families, or guilty feelings during the missions) might affect different subdomains of PTSD symptom improvement. Disaster rescuers should be followed up after their missions, regardless of their age, gender, or previous experience with disaster response. EMTs with certain personality characteristics or who are involved in specific field operations should be carefully monitored during and after disaster rescue missions.

The recent advances in satellite based ionosphere monitoring provided more evidence about earthquake (EQ) precursors from lithosphere ionosphere coupling mechanism. In this paper, we investigate ionospheric anomalies associated with the December 19, 2009, Taiwan EQ (Mw = 6.4), that occurred on UT = 13:02 h. Seismo ionospheric anomalies are evaluated during 31 days (20 day before followed by 10 days after the EQ) in the data of French Satellite Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and validated from Global Navigation Satellite System (GNSS) retrieved Total Electron Content (TEC). The day time values of ISL (Langmuir Probe) and IAP (Ion Analyzer) from DEMETER point to significant ionospheric perturbations within 5 days associated with EQ day. Moreover, GNSS stations of International GNSS Service (IGS) within EQ preparation zone also validate anomalies in ionosphere prior/after the Mw 6.4, Taiwan EQ. Moreover, spatial and temporal analyses of daily ionospheric indices from DEMETER and GNSS point to simultaneous enhancement in electron density, ion density, electron temperature and TEC related to the main shock during quiet geomagnetic storm (Dst < − 30 nT, Kp ≤ 3). All these evidence aids in promoting the lithosphere- ionosphere coupling over the epicenter of Mw 6.4 during the preparation period from DEMETER and GNSS TEC. [ABSTRACT FROM AUTHOR]

Taiwan is located along the boundary of the Eurasian and the Philippine Sea plates and experiences tens of thousands of earthquakes each year. Based on historical records, Taiwan has had several earthquakes of magnitude greater than 7.0. Notable and deadly quakes occurred in 1906 (Meishan Earthquake), 1935 (Hsinchu-Taichung Earthquake), and 1999 (Chi-Chi Earthquake). Statistically, Taiwan has had a major earthquake every 30–60 years. Therefore, earthquake museums are needed for long-term earthquake education and geoheritage exhibitions. Earthquake museums highlight disaster risks and preparedness information. The purpose of preserving earthquake remains is to educate visitors about Taiwan's natural disasters and provide a memorable experience that inspires earthquake preparedness. The Chushan trench across the Chelungpu fault is a good example of Chi-Chi Earthquake rupture. This trench has recorded the five most important earthquake events on the Chelungpu fault. Although the Chelungpu Fault Preservation Park (CFPP) has worked to preserve these earthquake remains, they have been threatened due to seepage over the years. The aim of this paper is to analyze trench seepage and explore the development of an anti-seepage model, to provide a reference for the preservation of earthquake remains and museum development worldwide. [ABSTRACT FROM AUTHOR]

Recently, researchers have conducted long-term statistical studies to prove the correspondence between earthquakes and thermal infrared (TIR) anomalies. Upon obtaining relatively high true positive rates (TPR), it was concluded that TIR anomalies are closely related to earthquakes. However, the temporal-spatial clustering of earthquakes and overly large temporal-spatial windows will also contribute to high TPRs, and it is improper to correlate TIR anomalies with earthquakes without excluding these influences. In this paper, relevant studies will be tested according to the prior probability, random earthquake catalogs and Molchan diagram weighted by the Relative Intensity (RI) index. Our results show that the high TPR in the previous studies were caused by overly large determining windows, and the result was close to random guessing, which means that the extracted TIR anomalies make no contributions to predicting the timing, epicenter and magnitude of earthquakes. By comparing the original Molchan diagram and the Molchan diagram weighted by the RI index, we found that simply taking the fraction of space-time occupied by alarm may give a wrong evaluation for alarm. Moreover, long-term statistical evidence proving the correspondence between earthquakes and TIR anomalies in Greece and Taiwan are still absent. [ABSTRACT FROM AUTHOR]

Resilience, which has rapidly become an area of interest in multiple disciplines, is regarded as being key in disaster mitigation and adaptation. The objective-indicator framework is a common way to evaluate resilience, but limited attention has been paid to measuring the risk perceptions and adaptation behaviors of individuals. In addition, due to limitations related to predicting potential earthquake events, past studies have placed more emphasis on predisaster discussions. Fortunately, this paper explores the changes in risk perceptions and adaptation behaviors in different socioeconomic groups through a comparative analysis between pre- and postearthquake disasters and through one-way analysis of variance (ANOVA) with a post hoc test applied to examine the changes in risk perceptions and adaptation behaviors. The results show that people tend to have greater risk perceptions of future earthquakes but are less willing to retrofit their houses after a serious disaster. Females show greater fear and worry accompanied by a higher willingness to retrofit their houses compared to males. In addition, people with a higher education level and a better occupation might be more willing than others to adopt adaptation behaviors. The results can serve as a reference to provide risk communication, risk education, and diverse disaster adaptation options. Although limitations exist, the results of comparative analysis between the predisaster and postdisaster conditions could serve as a reference for adequate strategies and government decisions on the prioritization of risk management policies. [ABSTRACT FROM AUTHOR]

Satellite measurements are becoming popular among the scientific community to identify earthquake precursors since its spatial coverage is more and round the clock measurements are possible. In this paper, we analyzed Total Electron Content (TEC), Outgoing Longwave Radiation (OLR), Sea Level Pressure (SLP), Surface Latent Heat flux (SLHF) and Sea Surface Temperature(SST) to identify any abnormal anomalies before Taiwan earthquakes which occurred on 4th February 2018 (M = 6.1, depth = 12 km) and 6th February 2018 (M = 6.4, depth = 17 km). The GPS data of International GNSS Service(IGS) stations (TWTF and CKSV) which operated 90 and 200 km away from the epicenter of the earthquake on 6th February 2018 respectively, were used for calculation of VTEC. The locations of these stations are within the preparatory zone of these earthquakes. The global parameters such as Dst, Kp, and IMF are also analyzed for the corresponding period of VTEC. We noticed the raise of temporal variations of 5–8 TECU before few days of the present earthquakes. The VTEC and other parameters such as SLP, SST, SLHF, and OLR were analyzed using the "Sliding Interquartile range method" during the period of 09th Jan to 10th Feb 2018 (33 days) to identify the abnormal signal due to these earthquakes. Strong positive anomalies occurred one day before the earthquake of 4th February and 1st, 3rd and 5th day before the Taiwan earthquake of 6th February 2018 with strong anomalous nature with an absolute amplitude of 5–8 TECU.The Cross wavelet analysis between Kp and TEC is carried out to study the impact of global geomagnetic activity on TEC during the seismic event and we found a negligible influence of global geomagnetic activity. The good raise of SLP on the day of the earthquake on 6th February 2018 have been noticed with the raise of 300 mb, the SLHF anomalies are observed at the interface of the earth's surface and atmosphere. Moreover, anomalous variations in air temperature and OLR were observed 2 days before the occurrence of the earthquake on 6th February 2018. Well co-ordinated scrutiny of various parameters such as TEC, SLHF, and OLR indicates that they can be used as promising precursors to the impending devastating earthquakes with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Variations of the ionosphere can significantly disrupt synthetic aperture radar (SAR) acquisitions and interferometric measurements of ground deformation. In this paper, we show how the ionosphere can also strongly modify C-band interferograms despite its smaller influence at higher frequencies. Thus, ionospheric phase screens should not be neglected: their compensation improves the estimation of ground deformation maps. The split-spectrum method is able to estimate the dispersive ionospheric component of the interferometric phase; we describe the implementation of this method for the burst modes TOPS and ScanSAR to estimate and remove ionospheric phase screens. We present Sentinel-1 interferograms of the 2016 Taiwan earthquake and ALOS-2 interferograms of the 2015 Nepal earthquake, which show strong ionospheric phase gradients, and their corrected versions. Finally, to validate the results and better understand the origin of these ionospheric variations, we compare the estimated differential ionosphere with global Total Electron Content maps and local Global Positioning System measurements. [ABSTRACT FROM PUBLISHER]

An earthquake with a magnitude of Mw=7.5 that occurred in Sulawesi, Indonesia, on 28 September 2018 triggered liquefaction and tsunamis that caused severe damage and many casualties. This paper reports the results of a post-tsunami field survey conducted by a team with members from Indonesia and Taiwan that began 13 d after the earthquake. The main purpose of this survey was to measure the run-up of tsunami waves and inundation and observe the damage caused by the tsunami. Measurements were made in 18 selected sites, most in Palu Bay. The survey results show that the run-up height and inundation distance reached 10.7 m in Tondo and 488 m in Layana. Inundation depths of 2 to 4 m were common at most sites and the highest was 8.4 m in Taipa. The arrival times of the tsunami waves were quite short and different for each site, typically about 3–8 min from the time of the main earthquake event. This study also describes the damage to buildings and infrastructure and coastal landslides. [ABSTRACT FROM AUTHOR]

Earthquake early warning system uses high-speed computer network to transmit earthquake information to population center ahead of the arrival of destructive earthquake waves. This short (10 s of seconds) lead time will allow emergency responses such as turning off gas pipeline valves to be activated to mitigate potential disaster and casualties. However, the excessive false alarm rate of such a system imposes heavy cost in terms of loss of services, undue panics, and diminishing credibility of such a warning system. At the current, the decision algorithm to issue an early warning of the onset of an earthquake is often based on empirically chosen features and heuristically set thresholds and suffers from excessive false alarm rate. In this paper, we experimented with three advanced machine learning algorithms, namely, $K$ -nearest neighbor (KNN), classification tree, and support vector machine (SVM) and compared their performance against a traditional criterion-based method. Using the seismic data collected by an experimental strong motion detection network in Taiwan for these experiments, we observed that the machine learning algorithms exhibit higher detection accuracy with much reduced false alarm rate. [ABSTRACT FROM AUTHOR]

Observations from recent earthquakes in Taiwan and Turkey have shown that current methodology to determine the liquefaction susceptibility of fine-grained soils is no longer sufficient to quantify seismic hazard, and that low plasticity fine-grained soils such as silts could also cause adverse effects on the performance of civil infrastructures. It is very important to understand the dynamic behavior of silt deposit because most of coastal areas, where there are many ongoing construction activities, consist mainly of silts, which might be vulnerable to earthquake loadings. This paper presents the experimental results of centrifuge tests on reconstituted specimen to investigate the dynamic response of normally consolidated deep silt deposit in Seattle area. The experimental sequence and preparation of the artificial silt deposit are described in detail. The recorded downhole accelerations are utilized to identify variation of shear modulus and damping ratio with shear strain amplitude via inverse analysis techniques applied to dense instrumentation arrays in a dynamic centrifuge model test. [ABSTRACT FROM AUTHOR]

Earthquake early warning systems assess the size of an earthquake based on initial ground motion and provide warnings before the arrival of large waves. We employ the iterative regression to simultaneously estimate the station correlations and the corresponding linear relations for magnitude. We report the standard error reductions of the magnitude estimation based on the initial peak P-wave acceleration (${P_a}$ P a ), velocity (${P_v}$ P v ), and displacement (${P_d}$ P d ) as $14.52\% $ 14.52 % , $7.63\% $ 7.63 % , and $7.58\% $ 7.58 % , respectively. Factor analysis of the stationary correction reveals its correlation with several factors. This study shows that station correction can help to improve the precision of magnitude estimation in the future. [ABSTRACT FROM AUTHOR]

This paper discusses plausible causes for the failure of a corner column in a 14-story reinforced concrete moment-frame building in Tainan, Taiwan, during the Meinong Earthquake of February 6, 2016. It is concluded that the failure occurred because of the effect of discontinuous partition walls. Nevertheless, the analyses presented suggest that, in strong ground shaking, the column would have been subjected to excessive axial compression even in the absence of said walls. [ABSTRACT FROM AUTHOR]

On February 6, 2015, a local magnitude (ML) 6.6 earthquake struck southern Taiwan, devastating the Tainan area. A field investigation was conducted by a survey team from the National Center for Research on Earthquake Engineering immediately after the earthquake. This paper summarizes the observed geotechnical damage features caused by the earthquake, including liquefaction, slope sliding, levee failure, and dam performance. Several liquefaction sites were observed despite the intensity of ground shaking being moderate (peak ground acceleration, ~0.2 g). Most of these sites were originally old ponds that were backfilled during different periods in the last three to eight decades. Two significant types of damage to the levee of the Tseng-wen River were observed. At the Jianshan site, a typical type of levee damage was observed, in which the level crest subsided and the side slope developed several cracks. At the Rixin site, a flow-type of failure caused tremendous loss of levee (~400 m in total) at three adjacent locations. The levee embankments had “flowed” up to 60 m into the river. [ABSTRACT FROM AUTHOR]

Liquefaction is one of the disasters caused due to earthquake. In 1999, Chi-Chi, Taiwan, earthquake is an example of liquefaction prone disasters induced due to Mw 7.6 earthquake. This becomes major cause for prediction of the liquefaction in the soil with respect to geotechnical property. In this paper, we have use Artificial Neural Networks (ANN) model based on Resilient Back propagation (Rprop), Decision tree model (DT) and classifier are C 4.5 and Random Forest is done for comparing the performance and evaluation of liquefaction potential based on the obtained field CPT data (Juang et al. [1]) consisting 125 datasets over the simplified procedures that are being traditionally use for the classification of liquefaction of the soil by different researchers. It is observe that Resilient Back propagation Algorithm prediction is 100% whereas C 4.5 algorithm and Random forest Algorithm are 97.6% and 98.4% accurate for the evaluation of seismic soil liquefaction potential. [ABSTRACT FROM AUTHOR]

Flat earthquake premiums are ‘uniformly’ set for a variety of buildings in many countries, neglecting the fact that the risk of damage to buildings by earthquakes is based on a wide range of factors. How these factors influence the insurance premiums is worth being studied further. Proposed herein is a risk‐based approach to estimate the earthquake insurance rates of buildings. Examples of application of the approach to buildings located in Taipei city of Taiwan were examined. Then, the earthquake insurance rates for the buildings investigated were calculated and tabulated. To fulfil insurance rating, the buildings were classified into 15 model building types according to their construction materials and building height. Seismic design levels were also considered in insurance rating in response to the effect of seismic zone and construction years of buildings. This paper may be of interest to insurers, actuaries, and private and public sectors of insurance. [ABSTRACT FROM AUTHOR]

In order to explore the correlation between earthquakes and ionospheric very low-frequency (VLF) electric field disturbances, this article uses VLF data observed by the China Earthquake Electromagnetic Satellite (CSES) to analyze very low-frequency signals before and after earthquakes from January 2019 to March 2023 in terms of the amplitude and signal-to-noise ratio of electric field power spectrum disturbances. Taking 73 earthquakes with a magnitude of 6.0 or higher occurring in the Circum-Pacific seismic belt as an example, comprehensive research on the VLF electric field disturbance phenomenon caused by strong earthquakes is conducted, considering both the earthquake location and source mechanism. The research results indicate the following: (1) there is a strong correlation between earthquakes with a magnitude of 6.0 or above and abnormal disturbances in the VLF electric field, which often occur within 20 days before the earthquake and within 800 km from the epicenter. (2) From the perspective of earthquake-prone areas, the VLF electric field anomalies observed before earthquakes in the Ryukyu Islands of the Taiwan region exhibit small and concentrated field fluctuations, while the Taiwan Philippines region exhibits larger field fluctuations and more dispersed fluctuations. The discovery of this correlation between seismic ionospheric phenomena and seismic activity provides a new and effective approach to earthquake monitoring, which can be used for earthquake prediction, early warning, and disaster prevention and reduction work. [ABSTRACT FROM AUTHOR]

The South China Sea faces widespread tsunami risks from diverse sources, including trench megathrusts, intraplate earthquakes, and landslides. However, historical and geological records to constrain worse-case simulations are scarce. The cliff-top basalt boulders on the Penghu Islands in the Taiwan Strait provide wave estimates from incipient motion formulas and stratigraphic links to the probable sources. Calibrating for ancient local sea levels and a 100-year surge indicates that storm waves in the shallow interisland bathymetry only enable boulder sliding–rolling below the 2.5 m high cliff. A minimum tsunami wave height of ∼ 3.2 m is necessary for cliff-top overflow to exceed boulder height and terminal rolling before deposition. Coeval gravels in two other outcrops also record the time and extent of tsunami deposition with beach-derived bioclasts, stranded pumices, a sharp base, matrix support, poor sorting, and elevations surpassing the 100-year surge. These gravels mark local minimum wave run-ups, reaching 2.4–4.0 m above sea level. The radiocarbon age of the studied boulder, between 1575 and 1706, suggests a probable tie to the disastrous 1661 earthquake in southwest Taiwan and the megathrust source in the northern Manila Trench. [ABSTRACT FROM AUTHOR]

Near-fault ground motion is a key to understanding the seismic hazard along a fault and is challenged by the ground motion prediction equation approach. This paper presents a developed stochastic-slip-scaling source model, a spatial stochastic model with slipped area scaling toward the ground motion simulation. We considered the near-fault ground motion of the 1999 Chi-Chi earthquake in Taiwan, the most massive near-fault disastrous earthquake, proposed by Ma et al. (2001) as a reference for validation. Three scenario source models including the developed stochastic-slip-scaling source model, meanslip model and characteristic-asperity model were used for the near-fault ground motion examination. We simulated synthetic ground motion through 3D waveforms and validated these simulations using observed data and the ground-motion prediction equation (GMPE) for Taiwan earthquakes. The mean slip and characteristic asperity scenario source models over-predicted the near-fault ground motion. The stochastic-slip-scaling model proposed in this paper is more accurately approximated to the near-fault motion compared with the GMPE and observations. This is the first study to incorporate slipped-area scaling in a stochastic slip model. The proposed model can generate scenario earthquakes for predicting ground motion. [ABSTRACT FROM AUTHOR]

Understanding the trajectories, drivers, and probabilities of land cover change can provide essential information for forested watershed planning and sustainable management. This paper demonstrates that the Taimali watershed in eastern Taiwan underwent a dramatic decrease in forest cover under the influences of frequent earthquakes and typhoons during 2005-2011. To grasp the dynamics of land cover change, this study applied a combined land-change analysis approach using trajectory analysis and logistic regression. The results of trajectory analysis indicate that three change trajectories, covering 75.65 % of the total changed area, were considered the major trends of alterations, including the trajectories of Forest-Landslide, Forest-Channel, and vegetation recovery. Based on the causes of land conversion, most land transformation resulted from natural causes. Therefore, natural forces play a pivotal role in land cover change in the Taimali watershed. The results of logistic regression analysis show that lithology is the most important spatial determinant for occurrence probability of three change trajectories, followed by aspect and slope. Three maps of occurrence probability of the change trajectories were produced using regression coefficients. With the validation of the relative change intensity index, the results reveal that the observed change trajectories considerably coincided with the zones that had higher probabilities of change and covered a small area. Thus, three spatial statistical models are helpful tools for projecting the occurrence probabilities of the change trajectories. [ABSTRACT FROM AUTHOR]

Motivated by an earthquake impact study, this paper develops new tests with several invariant properties for functional data. For multi-sample functional ANOVA (mfANOVA), based on local polynomial regression, exact local and global ANOVA decompositions into within- and between-group of variations are obtained. A local mfANOVA test is developed to examine differences in a local neighborhood, and combining local quantities, a global mfANOVA test statistic is formed. We show that both the local and global mfANOVA test statistics are location, scale, and translation invariant, allow interchanging the order of smoothing and ANOVA projection, and have asymptotic F -distributions under the null hypotheses with the Gaussian assumption. This paper contributes to the literature by being the first, to our knowledge, to study mfANOVA tests with several invariant properties. Simulation studies are presented to compare the proposed global mfANOVA test with some existing procedures. Application to an earthquake impact study in Taiwan reveals that when an earthquake in 2016 resulted in closed highways, the patterns of traffic flows were significantly different between three time periods, before the earthquake, during, and after the repair period. The information could be useful in planning for disaster preparedness. [ABSTRACT FROM AUTHOR]

Engineering risk assessment is to estimate the structure's failure probability multiplied by its failure consequences. On the other hand, the analysis was sometimes performed on a more general basis, utilizing a few indicators to quantify relative risk levels for decision-making. On the basis of such a framework, this paper introduces a novel risk assessment on 18 active faults in Taiwan, considering the fault's location, earthquake size and return period from the literature. The result shows that the Chelungpu Fault in central Taiwan has the highest risk score among the 18 active faults, in contrast to the Hengchun Fault in southern Taiwan which has the lowest risk. Besides this, the 18 active faults in Taiwan were classified into four groups based on this risk assessment, and the classification could help the region's sustainable development against earthquake hazard. [ABSTRACT FROM AUTHOR]

Resilience has rapidly arisen in multiple disciplines and has been regarded as the key in disaster mitigation and adaptation. Objective indicator framework is a common way evaluating resilience while limited attention on measuring subjective resilience. In fact, subjective resilience might further explain how people respond to the uncertainty of disaster risks. Due to the limitation on predicting potential earthquake events, past studies put more efforts on discussing pre-disaster. Luckily, this paper could explore the change of risk perception and adaptation behavior in types of socio-economic groups through a comparative analysis between pre- and post- earthquake disaster, and one-way analysis of variance with Post Hoc test is applied to examining the change of risk perception and adaptation behavior. The results show that female might be much willing on house retrofit due to the fear and the worrisome. However, the elders might be less aware on earthquake than the young. Education indeed affects people's risk perception and adaptive behavior. As a whole, the results could be referred to areas clustered of male, female, elder population, and lower education population by providing risk communication, risk education, and diverse disaster adaptation options. Although limitation exists, the results of comparative analysis between pre-disaster and post-disaster conditions could be referred to adequate strategies and decide the priority of risk management policies by governments. [ABSTRACT FROM AUTHOR]

It is well known that coseismic landslides are likely to occur under stronger shaking at shorter epicentral distance under the effects of topography and amplification of shaking together with such local geology as rock and soil types. However, this paper addresses a different issue that is the role of faults played in the triggering of landslides, both coseismic and non-seismic, and the long-term slope instability that lasts for decades or centuries after devastating earthquakes. Experiences during and after gigantic landslides are important to understand what happens in and around faults. Noteworthy is that there are cases in which slope instability starts after earthquakes and lasts for some time along surface manifestation of faults, whether or not they are the causative fault. Another important issue is the recovery of stability in shallow parts of slopes. Experiences in Japan, Taiwan and China suggest that a few decades is needed for this re-stabilization. Discussion is further made of geologically generated ground water pressure that is another causative mechanism of landslides. Thus, further field study is encouraged to promote slope hazard assessment. • Long-term slope instability after major earthquakes was studied by introducing examples in the past. • Compound effects of earthquake and rainfall on slope instability are presented. • Continuous slope instability along major tectonic lines is discussed. • Landslides triggered by abnormal ground water pressure are touched upon. • The concepts of process zone and geopressure should be investigated in more details. • The studied cases suggest the importance of more geological/geomorphological studies for understanding the landslide hazards in tectonically active regions of the world. [ABSTRACT FROM AUTHOR]

Understanding the kinematic characteristics of the Longitudinal Valley Fault Zone (LVFZ) can help us to better understand the evolution of orogens. The 2022 Mw7.0 Taitung earthquake that occurred in Taiwan provides us with a good opportunity to understand the motion characteristics of the Central Range Fault (CRF) and the strain partitioning pattern within the Longitudinal Valley Fault (LVF). We obtained the coseismic displacement and slip distribution of the 2022 Taiwan earthquake based on the strong-motion and GPS data available. The causative fault of this earthquake is the west-dipping Central Range Fault, which is buried beneath the western boundary of the LVF. The coseismic displacement field exhibits a quadrant distribution pattern, indicating a left-lateral strike-slip mechanism with a maximum displacement exceeding 1.25 m. The joint inversion results show that the size of the main asperity is 40 km × 20 km, and the maximum slip amount of 2.6 m is located at a depth of 10 km, equivalent to an earthquake of Mw7.04. The LVFZ is composed of LVF and CRF, which accommodates nearly half of the oblique convergence rate between the Philippine Sea Plate and the Eurasian Plate. There is a phenomenon of strain partitioning in the southern segment of the Longitudinal Valley Fault Zone. The Central Mountain Range Fault is primarily responsible for accommodating strike-slip motion, while the Longitudinal Valley Fault is mainly responsible for accommodating thrust motion. [ABSTRACT FROM AUTHOR]

The compression wave velocity (Vp) of sediments plays a key role in seismic wave amplification of vertical motion and is required in site response analysis. However, such information is usually lacking during field exploration (e.g. the surface wave method) because only shear wave velocity (Vs) is obtained. This aim of this study is to predict Vp based on Vs empirically and theoretically, particularly focusing on saturated conditions. The empirical approach is to establish the Vp correlation dependency on Poisson's ratio and Vs, and the theoretical approach is based on poroelastic theory that accounts for the interaction between fluid and soil skeleton. The engineering geological database for the Taiwan strong motion instrumentation program and the Kiban Kyoshin network database in Japan are adopted to establish an empirical model and validate poroelastic theory. The validated poroelastic approach is used to develop a constrained modulus reduction curve dependency on the porosity, Vs, Poisson's ratio and degree of saturation with a shear modulus reduction curve. The proposed approach can be used to develop generic Vp profiles and constrained modulus reduction curves for the site response to vertical motion given a site-specific Vs profile. [ABSTRACT FROM AUTHOR]

We investigate the temporal and spatial seismicity patterns prior to eight M > 6 events nucleating in different regions of Taiwan through a region–time–length algorithm and an analysis of a self-organizing spinodal model. Our results show that the spatiotemporal seismicity variations during the preparation process of impending earthquakes display distinctive patterns corresponding to tectonic settings. Q-type events occur in southern Taiwan and experience a seismic quiescence stage prior to the mainshock. A seismicity decrease of 2.5 < M < 4.5 events occurs around the relatively high b -value southern Central Range, which contributes to the accumulation of tectonic stress for preparing for the occurrence of the Q-type event. On the other hand, A-type events occur in central Taiwan and experience a seismic activation stage prior to the mainshock, which nucleates on the edge of the seismic activation area. We should pay attention when accelerating seismicity of 3 < M < 5 events appears within the low b -value area, which could promote the nucleation process of the A-type event. [ABSTRACT FROM AUTHOR]

In this paper, we study (1) the spatial anomalies and (2) the temporal anomalies of soil gas in northern Taiwan. The spatial anomalies of soil gas are related to tectonic faults, while the temporal anomalies of soil gas are associated with pre-earthquake activities. Detailed soil gas sampling was systematically performed, and the analysis of the collected gas species shows that high helium and nitrogen concentrations appear in samples from specific sites, which coincide with the structural setting of the area studied. This analysis indicates the possibility of using these soil gases to determine fault zones in the studied area. Based on the soil gas data, a station (Tapingti) for automatic soil gas monitoring was constructed on an appropriate site at the fault zone. Some anomalous high radon concentrations at certain times can be identified from the dataset, which was generated by the continuous monitoring of soil gas for over a year. Notably, many of these anomalies were observed several hours to a few days before the earthquakes (M L > 3) that occurred in northern Taiwan. By combining the information of epicenters and fault plane solutions of these earthquakes, we find that the shallow earthquakes (<15 km) were mainly strike-slip and normal-type earthquakes, and concentrated within a distance of 30 km to the monitoring site (Group A). The deep earthquakes (>20 km) were mainly thrust-type earthquakes and distributed in greater distances (>45 km) east of the monitoring site (Group B). Such focal mechanisms of earthquakes suggest an extensional and compressional structural domain in the continental crust for Group A and Group B earthquakes, respectively. It is suggested that the pre-earthquake activities associated with the seismicity of Group B may be transmitted along the major decollement in the region below the Tapingti station, leading to the observed soil gas enhancements. [ABSTRACT FROM AUTHOR]

This paper utilizes 10 stations of co-located seismometer, QuakeFinder/infrasound to observe co-seismic signatures triggered by the 6 February 2016 M 6.6 Meinong Earthquake. Each QuakeFinder system consists of a 3-axes induction magnetometer, an air conductivity sensor, a geophone, and temperature/relative humidity sensors. There are no obvious charges in the positive/negative ions, the temperature, and the humidity, while the magnetometer, the geophone, and infrasound data detect clear co-seismic signatures, similar to seismic waves recorded by seismometers. The magnetometers register high-frequency pulsations, like seismic waves, and superimpose with low-frequency variations, which could be caused by the magnetometer shaking/tilting and/or the underground water level change, respectively, upon the arrival of seismic waves. The spectrum centering around 2.0 Hz of the co-seismic geophone fluctuations is similar to that of the seismic waves. However, the energy of co-seismic geophone fluctuations (also magnetometer pulsations) yields an exponential decay to the distance of a station to the epicenter, while the energy of the seismic waves is inversely proportional to the square of the distance. This suggests that the mechanisms for detecting seismic waves of the QuakeFinder system and seismometers are different. In general, the geophone and magnetometer/infrasound system are useful to record high- and low-frequency seismic waves, respectively. [ABSTRACT FROM AUTHOR]

Many earthquake empirical models were developed based on the statistics in the past. However, it is commonly seen that a non-local model was applied to a local study without any adjustment. In this paper, a new algorithm using maximum likelihood estimation (MLE) to adjust a non-local model for local applications was presented, including a case study assessing the probability of major earthquake occurrences in Taipei. Specifically, considering the fault length of 36 km and slip rate of 2 mm/yr, it suggests the Sanchiao (or Shanchiao) fault could induce a major earthquake with magnitude M w 7.14±0.17, based on a non-local model integrated with limited local data using the MLE algorithms. [ABSTRACT FROM AUTHOR]

We analyze high-resolution borehole strainmeter signals to constrain the fault plane solutions and locations of the 2009 Fengpin-Hualien earthquakes, in eastern Taiwan. The December M w 6.6 earthquake has ruptured a narrow section of the Collision Seismic Zone (within depth of 34 to 44 km), an active structure located offshore northeast Taiwan. The October M w 6.3 event has ruptured the deep section of the Longitudinal Valley fault (25–32 km depth) located between Fengpin and Fanglin. Coulomb stress changes induced by the October event in the hypocenter region of the December event are low (< +30 kPa), which suggests that the latter event was not induced by static stress transfer. The December event is characterized by an abundant seismicity for about 2.5 days following the mainshock. The temporal evolution between the aftershock rate and geodetic strain suggests that seismicity could have been controlled by a short-lived frictional afterslip. Besides, we infer that significant positive static Coulomb stress changes (> +100 kPa) induced by this sequence at shallow to moderate depths in the Longitudinal Valley (0–12 km) may have influenced the occurrence of large mainshocks in eastern Taiwan during the past decade. Conversely, limited stress (< +30 kPa) is transferred to the shallow, locked section of the southernmost Ryukyu trench. This study emphasizes the importance of borehole strain measurements in active regions to enhance detection of seismic and aseismic events unresolved by surface geodesy. [ABSTRACT FROM AUTHOR]

The strong Hualien earthquake (Mw 6.1) occurred along the suture zone of the Eurasian Plate and the Philippine Sea Plate, which struck the Hualien city in eastern Taiwan on April 18, 2019. The focal mechanism of this earthquake shows that it is caused by a rupture within a thrust. In the present study, the rupture plane responsible for this earthquake has been modeled using the modified semi-empirical technique (MSET). The whole rupture plane is assumed to be composed of strong motion generation areas (SMGAs) along which the slip occurs with large velocities. The spatiotemporal distribution of aftershocks of this earthquake within identified rupture plane suggests that there are two SMGAs within the rupture plane. The source displacement spectra (SDS) obtained from the observed records have been used to compute the source parameters of these two SMGAs. The MSET efficiently simulates strong ground motion (SGM) at the rock site. The shallow subsurface shear wave velocity profile at various stations has been used as an input to SHAKE91 algorithm for converting records at the surface to that at the rock site. The simulated records are compared with the observed records based on root-mean-square error (RMSE) in peak ground acceleration (PGA) of horizontal components. Various parameters of the rupture plane have been selected using an iterative forward modeling scheme. The accelerograms have been simulated for all the stations that lie within an epicentral distance ranging from 5 to 100 km using the final rupture plane parameters. The comparison of observed and synthetic records validates the effectiveness of the simulation technique and suggests that the Hualien earthquake consists of two SMGAs responsible for high-frequency SGM. [ABSTRACT FROM AUTHOR]

The M w 7.6 Chi-Chi earthquake struck central western Taiwan in 1999. The rupture was complex with several dislocations along the 100-km long Chelungpu thrust fault. Revisiting this earthquake is a challenge, as the precision and coverage of the data sets available are quite poor. Furthermore, the topographic and vegetation coverage complexity of the area prevents coherent radar images. In this paper, radar and optical images, and terrestrial geodetic measurements, were utilised to study the fault. The Particle Swarm Optimization and Okada Inversion (PSOKINV) geodetic inversion package was used with the generalized Akaike's Bayesian Information Criterion (gABIC) to precisely determine the slip distribution and relative weighting of datasets. Differences in results using the data sets jointly or separately (e.g., under-estimation due to InSAR, inconsistencies in SPOT offsets, smoother slip distribution with gABIC weighting) are observable. Most of the energy was released in the northern part of the fault, where the strike veers toward the east, and mainly at depths less than 4 km. The PSOKINV-gABIC approach is viable for the study of complicated cases such as the Chi-Chi earthquake and can significantly benefit the weight determination and physical realism of the fault geometry. [ABSTRACT FROM AUTHOR]

This paper presents the first whole Taiwan-scale spatial variation of the seismogenic zone using a high-quality crustal seismicity catalog. The seismicity onset and cutoff depths (i.e., seismogenic depths) are determined by the earthquake depth–moment distribution and used to define the upper and lower boundaries of the seismogenic zone, respectively. Together with the published fault geometries and fault area–moment magnitude relations, the depth difference in the onset and cutoff depths (i.e., seismogenic thickness) is used as the fault width to determine the moment magnitudes of potential earthquakes for the major seismogenic faults. Results show that the largest ( Mw 7.9–8.0) potential earthquake may occur along the Changhua fault in western Taiwan, where the seismic risk is relatively high and seismic hazard mitigation should be a matter of urgent concern. In addition, the first-motion focal mechanism catalog is used to examine the relation between the seismogenic depths and earthquake source parameters. For crustal earthquakes (≤ 50 km), the shallowest onset and cutoff depths are observed for normal and strike-slip events, respectively. This observation is different from the prediction of the conventional continental-rheology model, which states that thrust events have the shallowest cutoff depth. Thus, a more sophisticated rheology model is necessary to explain our observed dependence of the seismogenic depths on faulting types. Meanwhile, for intermediate to large crustal ( Mw ≥ 4; depth ≤ 50 km) earthquakes, thrust events tend to occur at the bottom region of the seismogenic zone, but normal and strike-slip events distribute at a large depth range. [ABSTRACT FROM AUTHOR]

Earthquake early warning (EEW) has been implemented in several regions around the world. However, because of natural randomness and uncertainty, false alarm and missed alarm can be expected in EEW. The key scope of this study is to evaluate the reliability of an on-site EEW in Taiwan, by testing the system's algorithm with 17,836 earthquake data from 1999 to 2013. The analysis shows that the on-site EEW system, empirically speaking, should have a false-alarm probability of 2.5%, and a missed-alarm probability of 14.1%. Considering missed alarm should be more critical to EEW, a new algorithm that could reduce the system's missed-alarm occurrences to 6% is also discussed in this paper. [ABSTRACT FROM AUTHOR]

Sustained coseismic changes in groundwater level due to static strain during earthquakes could be considered as an indicator of crustal deformation. These changes usually occur abruptly but recover slowly after earthquakes. High-frequency data indicate a time lag between the coseismic change of well water levels and that of the groundwater levels in the aquifer. Abnormal post-seismic changes in groundwater level were observed, possibly caused by cross-formation flow, fracturing, or strain relief. Although sustained changes are generally induced by a local earthquake, they could also be triggered by a distant large earthquake that has occurred at the same tectonic plate. The magnitude and polarity of coseismic changes may vary in wells of different depths at multiple-well stations, revealing additional information about the complexity of crustal deformation in the subsurface. Coseismic falls dominated near the ruptured seismogenic fault during the 1999 M7.6 earthquake, which implied crustal extension adjacent to the thrust fault. However, coseismic rises prevail in most areas, suggesting that crustal compression caused by plate convergence plays a major role on the island of Taiwan during earthquakes. [ABSTRACT FROM AUTHOR]

The ground vibrations observed in Taiwan during three teleseismic earthquakes in 2011 by broadband seismometers near major science parks were investigated. Their frequency content was exhibited via spectral analysis, and their effect on structures was examined by response spectra. To assess their possible impact on vibration-sensitive facilities, three vibration criteria in terms of velocity or displacement were utilized. Their predominant frequencies were between 0.04– and 0.16 Hz and somewhat dependent on focal depth and site geology, and they were therefore only influential to very long-period structures. However, the vibration levels exceeded the adopted criteria to some extent, especially at the softer site. [ABSTRACT FROM AUTHOR]

Seismically active fault zones are complex natural systems and they exhibit multifractal correlation between earthquakes in space and time. In this paper, the seismicity of the Taiwan seismic region was studied through the multifractal characteristics of the spatial-temporal distribution of earthquakes from 1st January 1995 to 1st January 2019. We quantified the multifractal characteristics of Taiwan at different scales and defined them as ΔD values. Furthermore, we studied the relationship between the ΔD and b values, which signifies the average size distribution of those earthquakes. The results are as follows. (1) The temporal multifractal curve changes substantially before and after the strong earthquakes. (2) The maximum ΔD value of the seismic region in Taiwan occurs at depths of 0~9 km, indicating that geological structures and focal mechanisms is the most complex at these depths compared with other depths. (3) ΔD values for different regions range from 0.2~1.5, and b values range from 0.65~1.3, with a significant positive correlation between them (ΔD = 1.5 × b − 0.68). For this purpose, a statistical relationship is developed between b and ΔD values, and regional and temporal changes of these parameters are analyzed in order to reveal the potential of future earthquakes in the study region. [ABSTRACT FROM AUTHOR]

Lateral spreading of an interlayered deposit adjacent to a meandering stream channel in Wufeng, Taiwan, during the 1999 Chi-Chi Earthquake is evaluated using two-dimensional (2D) nonlinear dynamic analyses (NDAs) with geostatistical modeling of the subsurface to assess their ability to approximate the observed magnitude and spatial extent of ground deformations, as well as identify the key factors and mechanisms that most contributed to the overall system response. In-situ data from borings and cone penetration tests (CPTs) depict thinly stratified overbank deposits of low-plasticity silty sands, silts, and clays, interlayered with laterally discontinuous channel-deposited sands. The three-dimensional (3D) subsurface is simulated using transition probability-based indicator geostatistics, conditioned on available CPT data and geological inferences. The NDAs are performed using the PM4Sand and PM4Silt constitutive models, within the FLAC finite difference program. Sensitivity analyses are performed to understand the influence of uncertainties in the stratigraphy, channel conditions, soil properties, input ground motions, constitutive model calibration protocols, and numerical boundary conditions, as well as the performance of alternate channel transects. Most analysis cases generally matched the maximum displacements observed near the channel but overestimated the extent of displacements away from the channel. The most favorable results were largely influenced by nonstationary stratigraphic trends and cyclic softening of fine-grained soils, in addition to the liquefaction of coarse-grained soils. This case history demonstrates the capabilities and limitations of current subsurface and NDA modeling procedures for predicting ground deformation patterns. [ABSTRACT FROM AUTHOR]

Total electron content (TEC) precursors of the Chi-Chi Earthquake, which occurred in Taiwan at 01:47:15 on September 21, 1999 (Taiwan Standard Time, TST), with its epicenter at 23.85° N and 120.82° E, a Richter magnitude (ML) of 7.3 (a moment magnitude (Mw) of 7.6), and a focal depth of 8.00 km, were detected 1, 3, and 4 days before the earthquake using two back-propagation neural network (BPNN) models. These results are consistent with the analysis results of Liu et al. (2001) and Lin (2010). Another TEC precursor was detected on May 13, 2003 (TST), 2 days before the earthquake on May 15, 2003 (TST), with an ML of 5.21. Their precursors might be induced by the variations of the geomagnetic and electric fields near their hypocenter. The two BPNN models were to be verified for stability and reliability after performing cross-validation and evaluating the variance in the learning process. For this, the result of the analyzed method can serve as a real-time TEC predicted system for giving any future time as inputs of the two BPNN models. Hence, an earthquake early warning (EEW) system is performable. [ABSTRACT FROM AUTHOR]

A short‐term (30 days before an earthquake) prediction of an earthquake is a big challenge in seismology. As a first step, we apply deep learning to the ionospheric total electron content (TEC) data between 2003 and 2014 to detect the seismo‐ionospheric precursors of M ≥ 6.0 earthquakes in Taiwan. The bidirectional Long Short‐Term Memory (Bi‐LSTM) network is employed to use observed input data (features) to obtain the sequential TEC variations. The five input features are sequential vectors of TEC, the geomagnetic index Dst, the solar activity index F10.7, sunspot number (SSN), and solar emission index Lyman‐α. The daily values of F10.7, SSN, and Lyman‐α are converted into hourly values, depending on the solar elevation angle. The calculated hourly TEC variations can be more precisely predicted with this data conversion. We calculate the normalized difference of errors between two 15‐day adjacent stages as the "relative error". Three trained models with the best discrimination between the relative errors of earthquake and no‐earthquake cases are chosen as classifiers. These three classifiers are then used to have a majority vote to declare whether the 30‐day period is related to the preparation of an earthquake or not. The results show that all 22 positive cases (earthquakes) are successfully predicted, giving a true positive rate of 100%. Among the 19 negative cases (normal cases), 10 of them are true negative." Overall, a high accuracy of 78.05% is obtained. Plain Language Summary: A short‐term (30 days before an earthquake) prediction of earthquake is a big challenge in seismology. As a first step, we apply deep learning to the ionospheric total electron content (TEC) data, solar activity and geomagnetic data between 2003 and 2014 to detect the seismo‐ionospheric precursors of magnitude M ≥ 6.0 earthquakes in Taiwan. The deep learning method is employed to use the running 7‐day observed data to predict the next hour TEC value. The seismo‐ionospheric precursors can be identified by the normalized difference between the predicted TEC and the observed TEC data. The results show that all 22 positive cases with M ≥ 6.0 earthquakes are successfully predicted, while 10 of 19 negative cases without M ≥ 5.3 earthquakes are correctly predicted "No". A high accuracy of 78.05% is obtained. Key Points: Deep learning is applied to the detection of ionospheric precursors associated with M ≥ 6.0 earthquakes between 2003 and 2014 in TaiwanAll positive cases are successfully predicted, while 10 of 19 negative cases are predicted "NO". A high accuracy of 78.05% is obtainedThere is no occurrence of M ≥ 5.3 earthquake when the trained models predict "NO". The false rate is 0% [ABSTRACT FROM AUTHOR]