Future Large Earthquake Analysis of Sulawesi Island Using Satellite Images and Moment Tensor Solution Approach

Sulawesi Island is the active tectonic region, where the tectonic architecture and potential earthquake sources until now remain largely unknown. The worst earthquake, an Mw 7.5 on September 28, 2018, in Palu, Indonesia, was caused catastrophic damage to life and property. The earthquake has highlighted the urgent need to raise knowledge of the cause of possible large future earthquakes and vulnerability. The main objective for this project is to create a thorough earthquake probabilistic hazard analysis map of the region, which is presently unavailable to better prepare for future earthquakes. The neotectonic and structural map was created using was supplemented with the 30-m resolution Shuttle Radar Topography Mission, Centroid Moment Tensor (CMT) solution, and seismologic data. The results demonstrate that faulting controls the geometry and the majority of these faults are active and capable of causing medium to large magnitude earthquakes with moment magnitudes ranging from 6.2 to 7.5 from 44 seismic sources. Our results show Sulawesi's northern deformation regimes have high seismicity risk and vulnerability. This study contributes a realistic seismic source for the Sulawesi neotectonic area particularly at the northwest, north, and east deformation regime, to understand the key large future earthquakes.

The Source Characteristics of the Mw6.4, 2016 Meinong Taiwan Earthquake from Teleseismic Data Using the Hybrid Homomorphic Deconvolution Method

The kinematic source rupture process of the 2016 Meinong earthquake (Mw = 6.4) in Taiwan was derived from apparent source time functions retrieved from teleseismic S-waves by using a refined homomorphic deconvolution method. The total duration of the rupture process was approximately 15 s, and one slip-concentrated area can be represented as the source model based on images representing static slip distribution. The rupture process began in a down-dip direction from the fault toward Tainan City, strongly suggesting that the rupture had a unilateral northwestern direction. The asperity with an area of approximately 15 × 15 km2 and the maximum slip of approximately 2 m were centered 12.8 km northwest of the hypocenter. Coseismic vertical deformation was calculated based on the source model. Compared with the results derived from InSAR (Interferometric Synthetic Aperture Radar) data, our results demonstrated that the location with maximum uplift was accurately well detected, but our maximum value was just approximately 0.4 times of the InSAR-derived value. It reveals that there are the other mechanisms to affect the vertical deformation, rather than only depending on the source model. At different depths, areas west, east, and north of the hypocenter maintained high values of Coulomb stress changes. This explains the mechanism behind aftershocks being triggered and provides a reference for predicting aftershock locations after a large earthquake. The estimated seismic spectral intensities, including spectral acceleration and velocity intensity (SIa and SIv), were derived. Source directivity effects caused damage to buildings, and we concluded that all damaged buildings were located within a SIa value of 400 gal. Destroyed buildings taller than seven floors were located in an area with a SIv value of 30 cm/s. These observations agree with those on damages caused by the 2010 Jiasian earthquake (ML 6.4) in Tainan, Taiwan.

A morpho-tectonic approach to the study of earthquakes in Rome

Rome has the world’s longest historical record of felt earthquakes, with more than 100 events during the last 2,600 years. However, no destructive earthquake has been reported in the sources and all of the greatest damage suffered in the past has been attributed to far-field events. While this fact suggests that a moderate seismotectonic regime characterizes the Rome area, no study has provided a comprehensive explanation for the lack of strong earthquakes in the region. Through the analysis of the focal mechanism and the morphostructural setting of the epicentral area of a "typical" moderate earthquake (ML = 3.3) that recently occurred in the northern urban area of Rome, we demonstrate that this event reactivated a buried segment of an ancient fault generated under both a different and a stronger tectonic regime than that which is presently active. We also show that the evident structural control over the drainage network in this area reflects an extreme degree of fragmentation of a set of buried faults generated under two competing stress fields throughout the Pleistocene. Small faults and a present-day weaker tectonic regime with respect to that acting during the Pleistocene explain the lack of strong seismicity and imply that a large earthquake could not reasonably occur.

Tectonic Geomorphic of Sulawesi Island and Its Implication for Future Large Earthquake

This paper analyzes how resource of past and prospective great earthquake on the Central Sulawesi Arm, adhere on topography analysis from several space-based source. To answer the question, we analysis the tectonic geomorphic, stream pattern, exhumed fault, geological mapping and seismicity data. Detailed tectonic geomorphic studies in Sulawesi still lacking due to tectonic and fault obscures. For instance, Palu Koro Fault (PKF) was unpredictable, because the historical seismic records inevitably remain poorly documented and unrecognized fault strand, which was buried beneath abundant Quaternary alluvium subsequently obscured the fault trace. In other hand, the faults have been active during Quaternary must take into account because potentially dangerous, also the inactive faults during instrumental period must be re-evaluated in order to have awareness for large future large earthquake. Surprisingly, recent seismic activity of PKF generate super shear rupture a Mw 7.5 earthquake on 28th September 2018 with average slip 41 mm/year, which over the past two decade quiet from any seismic activity. The seismic potential for large fault is essential, since it has been silent during the instrumental period. Therefore, our motivation in this study to produce detail tectonic geomorphic map of the region in local scale, which is currently not available to prepare better knowledge and awareness for the large future earthquake. We have use Shuttle Radar Topography Mission (SRTM) with resolution ~30m, which run by ArcGIS software to observed tectonic geomorphic evidence of fault system and supplement with structural, geological and bathymetric data’s as ware available to us. We relate this analysis with seismicity data from Centroid Moment Tensor Solution (CMT) to recognize the seismic source. Our results show the tectonic geomorphic of Central Sulawesi Arm due to nature extension of NNW-SSE left-lateral slip curving to WNW-ESE of Palu-Koro Fault (PKF), then transcript to N-S circular normal fault of Poso Fault (PF). The PF indicate replica of PKF curving, where has not been mapped previously. We have mapped 60 major onshore fault systems, 10 faults showed evidence maximal to rapid rate tectonic activity along instrumental periods. Based on our CMT analysis, Sulawesi Island is greatly dominated by oblique fault.

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

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

Statistics of the earthquakes in the central Himalaya and its vicinity in last 56 years, with an emphasis in the 25 April 2015 Gorkha, Nepal earthquake

To understand the variation of stress levels in the region 80°E – 89°E and 26°N – 31°N, the statistical analysis of earthquake frequency-magnitude distribution and spatio-temporal variation of fractal correlation dimension of earthquake epicenter distribution are estimated. The analysis is carried out on declusterised catalogue containing 1185 events of 56 years from February 1964 to November 2020. The study area is divided into three regions the western Nepal and vicinity (Region A), central Nepal and vicinity (Region B) and eastern Nepal and vicinity (Region C), respectively. The magnitude of completeness (Mc) varies from 3.6 to 4.0 for the study period. The spatial fractal dimension (Dc) and b-value are calculated as 1.89 ± 0.02 and 0.68 ± 0.03 for the western Nepal, 1.76 ± 0.01 and 0.60 ± 0.05 for the central Nepal, whereas they are estimated as 1.85 ± 0.02 and 0.63 ± 0.03 for the eastern part of the Nepal. The b-values obtained for all three regions are very low comparing to global average value of 1. The time clustering of the events in the respective regions are 0.26 ± 0.003, 0.31 ± 0.004 and 0.26 ± 0.02 as indicated by temporal fractal dimension (Dt). The higher Dc, lower b and Dt values associated with the regions indicate high stress concentration and stronger epicenter clustering in these regions. The strongly increasing trend of fractal dimension and strongly decreasing trend of b-value show the high probabilities of occurring the large earthquake in both central Nepal (82.5°E – 85.5°E and 27.5°N – 30°N) and eastern Nepal (85.5°E – 88.2°E and 26.45°N – 28.6°N) as compared to western Nepal (80°E – 82.5°E and 28°N – 30.5°N). This statistical analysis of spatial and temporal characteristics of the earthquake activity may give significant signs of the future seismic hazard along central Himalaya region.

Testing the Synchronicity of Splay-Fault Ruptures in Carson Valley, Nevada, United States

ABSTRACT The Carson City and Indian Hills faults in Carson City, Nevada, splay northeastward from the major range-bounding Genoa fault. Each splay is part of the Carson range fault system that extends nearly 100 km northward from near Markleeville, California, to Reno, Nevada. Stratigraphic and structural relationships exposed in paleoseismic excavations across the two faults yield a record of ground-rupturing earthquakes. The most recent on the Carson City fault occurred around 473–311 B.P., with the two penultimate events between 17.9 and 8.1 ka. Two trench exposures across the Indian Hills fault record the most recent earthquake displacement after ∼900 yr, preceded by a penultimate surface rupture ≥∼10,000, based on radiocarbon and infrared-stimulated luminescence dating of exposed sediments. The age estimates allow that the Carson City and Indian Hills faults ruptured simultaneously with a previously reported large earthquake on the Genoa fault ∼514–448 B.P. Similar synchronicity of rupture is not observed in the record of penultimate events. Penultimate ages of ruptures on the Carson City and Indian Hills faults are several thousand years older than that of the Genoa fault from which they splay. Together, these observations imply a variability in rupture moment through time, demonstrating the importance of considering multi-fault rupture models for seismic hazard analyses.

Rapid Estimation of Earthquake Magnitude and Source Parameters Using Genetic Algorithms

To minimize the impacts of large losses and optimize the emergency response when a large earthquake occurs, an accurate early warning of an earthquake or tsunami is crucial. One important parameter that can provide an accurate early warning is the earthquake’s magnitude. This study proposes a method for estimating the magnitude, and some of the source parameters, of an earthquake using genetic algorithms (GAs). In this study, GAs were used to perform an inversion of Okada’s model from earthquake displacement data. In the first stage of the experiment, the GA was used to inverse the displacement calculated from the forward calculation in Okada’s model. The best performance of the GA was obtained by tuning the hyperparameters to obtain the most functional configuration. In the second stage, the inversion method was tested on GPS time series data from the 2011 Tohoku Oki earthquake. The earthquake’s displacement was first estimated from GPS time series data using a detection and estimation formula from previous research to calculate the permanent displacement value. The proposed method can estimate an earthquake’s magnitude and four source parameters (i.e., length, width, rake, and slip) close to the real values with reasonable accuracy.

SafeNet: SwArm for Earthquake Perturbations Identification Using Deep Learning Networks

Low Earth orbit satellites collect and study information on changes in the ionosphere, which contributes to the identification of earthquake precursors. Swarm, the European Space Agency three-satellite mission, has been launched to monitor the Earth geomagnetic field, and has successfully shown that in some cases it is able to observe many several ionospheric perturbations that occurred as a result of large earthquake activity. This paper proposes the SafeNet deep learning framework for detecting pre-earthquake ionospheric perturbations. We trained the proposed model using 9017 recent (2014–2020) independent earthquakes of magnitude 4.8 or greater, as well as the corresponding 7-year plasma and magnetic field data from the Swarm A satellite, and excellent performance has been achieved. In addition, the influence of different model inputs and spatial window sizes, earthquake magnitudes, and daytime or nighttime was explored. The results showed that for electromagnetic pre-earthquake data collected within a circular region of the epicenter and with a Dobrovolsky-defined radius and input window size of 70 consecutive data points, nighttime data provided the highest performance in discriminating pre-earthquake perturbations, yielding an F1 score of 0.846 and a Matthews correlation coefficient of 0.717. Moreover, SafeNet performed well in identifying pre-seismic ionospheric anomalies with increasing earthquake magnitude and unbalanced datasets. Hypotheses on the physical causes of earthquake-induced ionospheric perturbations are also provided. Our results suggest that the performance of pre-earthquake ionospheric perturbation identification can be significantly improved by utilizing SafeNet, which is capable of detecting precursor effects within electromagnetic satellite data.

Effect of Building Configuration on Overstrength Factor and Ductility Factor

It is important for the structure to be economical and still have a high level of life safety. The lateral force sustained by the structures during a large earthquake would be several times larger than the lateral force for which the structures are designed. This is opposite to the fact that design loads such as gravity in codes are usually higher than the actual anticipated load. It is based on the probability that the occurrence of large earthquakes is quite rare and the capacity of the structure to absorb energy. The co-factors of response reduction factor which is the overstrength factor and ductility factor reduce the design horizontal base shear coefficient. A total of 36 low-rise residential buildings having different storey, bay and bay lengths are selected and analysed in this paper. NBC 105: 2020 is selected for the seismic design of RC buildings while provision provided in FEMA 356:2000 is used to carry out non-linear pushover analysis. The results indicated that between the different structures, the value of overstrength factor and ductility factor has a high deviation.