Big Earthquake Research Articles

An Aftershock Deletion Method Based on Fault Buffer Zone

The existence of aftershocks in an earthquake sequence can impact the analysis of the mainshock. In this study, we present a method for deleting an aftershock sequence based on the spatial relationship between earthquakes and faults. This method improves the performance of space window selection in the classical K-K method by eliminating aftershocks with an ideal fault buffer zone. The determination of fault buffer zones is based on a trial-and-error analysis of 69,714 earthquake records from the China Seismic Network Center (CENC) collected between 1980 and 2020. We selected 20 typical big earthquakes (ML7.0–8.0 or ~Ms6.6–8.0; for earthquakes above magnitude Ms7 or ML7.2, ML is approximately equal to Ms) as the mainshocks to establish the fault buffer zones. We also propose an empirical formula to determine the distance of the fault buffer zone by counting the aftershock deletion effect at different buffer distances. Compared with the classical K-K method, our method considers the correlation between the spatial distribution of aftershocks and faults, eliminates earthquake groups that are not related to the mainshock, greatly reduces the spatial range of aftershocks, improves the performance of deleting aftershocks of different magnitudes, and provides a new rule and reference for aftershock deletion.

How does lithospheric viscosity control the temporal patterns of seismicity during an earthquake cycle?

The temporal patterns of regional seismicity, such as acceleration and deceleration patterns of seismic moment release, Benioff strain release, or number of earthquakes over time before a big earthquake or between two big earthquakes, have been observed in various regions. However, the mechanisms or controlling factors to cause these temporal patterns of seismicity have not been fully clarified. In this study, we collect, summarize, and analyze temporal patterns of regional seismicity (acceleration and deceleration patterns) in the world and observe a statistical relation between them and regional lithospheric viscosity values. We also develop and use a three-dimensional viscoelastoplastic finite-element model and an analytical model, to investigate and explain the importance of lithospheric viscosity on temporal patterns of seismicity during an earthquake cycle. We find that viscosity in lower crust and upper mantle can control seismicity acceleration and deceleration patterns during an earthquake cycle: low viscosity tends to cause deceleration pattern because fast postseismic stress accumulation within upper crust due to fast stress relaxation in viscoelastic layers following an earthquake induces frequent occurrence of regional earthquakes at early stage of an earthquake cycle, but on the contrary, high viscosity encourages acceleration pattern with frequent occurrence of regional earthquakes at late stage of an earthquake cycle. Between the low and high viscosity, a transitional viscosity zone roughly ranging from ∼1 × 1019 to ∼1 × 1020 Pa s exists. When average viscosity in lower crust and upper mantle stays in this range, regional seismicity acceleration and deceleration patterns can coexist at similar percentages and it is statistically hard to distinguish which pattern dominates in the region. Regional tectonic loading velocity also has an impact on temporal patterns of seismicity during an earthquake cycle: slow tectonic loading velocity tends to induce seismicity deceleration pattern, but fast tectonic loading velocity encourages seismicity acceleration pattern.

Analysis of Coulomb Stress Changes in Aceh Earthquake on Sibayak Volcano

Based on geological conditions, Indonesia is located between the Indo-Australian plate, the Eurasian plate, and the Pacific plate, making Indonesia prone to tectonic earthquakes. However, since the big earthquake that occurred in Aceh on December 26, 2004, the geological conditions in Sumatra have undergone significant changes marked by stressful situations in the western to southern regions of Sumatra, especially on Sibayak Volcano. This study used data from BMKG and Global CMT, which included magnitude (Mw), depth, earthquake coordinates (longitude and latitude), type of earthquake, strike, dip, and rake. From the analysis using Coulomb 3.3, the highest coulomb stress value of Sibayak Volcano was obtained in 2015 with an average change in coulomb stress of 0.235 bar, shear 0.1909 bar, normal 0.1106 bar. However, the lowest coulomb stress value occurs in 2021 with a moderate shift in coulomb stress of 0.0593 bar, shear 0.0251, normal 0.0849 bar.

Penguatan Kapasitas Kelompok Tani Hortikultura dalam Pengembangan Bisnis Pembibitan di Desa Pendua Kabupaten Lombok Utara

Horticulture is an importance farming system in North Lombok due to two reasons, first it provides job to the community, and second it becomes a source of households’ income which is different from food crops. A collaborative project between Mataram University and Massey University – New Zealand called as IFSCA Project (2017 – 2020) has facilitated the adoption and diffusion of horticultural innovations in North Lombok, however two natural disaster, namely earth quake (in mid 2018) and covid-19 pandemy (early 2020) had disturbed the horticulture farming system. The big earth quake destroyed the irrigation channels and some water springs disappeared while the covid-19 pandemy had led to farmers’ difficulties to sell their horticulture products, and a results farmers’ production and incomes decreased significantly. This public service activity was conducted in September 2021 to help farmers addressing issues associated with these horticulture farming system issues. Based on the evaluation results, it was found that farmers’ knowledge and outlooks had improved due to the activity – strengthening the capacity of farmers and farmer group, especially in the area of farming management, the importance of partnership, doing extra-services to the customers, product quality and guarantee, the existence of horticulture clinic), and critical support from the agency such as North Lombok Horticulture Development Agency. This institution has played critical roles in horticulture agribisnis system development, ranging from the input system to the marketing systems of the products, for both seedling and horticulture products. This article presents a summary of the public service activities and results conducted in North Lombok at Pendua Village – Kayangan Subdistrict – North Lombok.

Earthquake Threats in Ranau – From The Sources of Mensaban and Mesilou Fault

Unlike the majority of Malaysia’s other states, Sabah is characterised by frequent seismological activity; on average, an earthquake of moderate magnitude occurs roughly every 20 years, originating primarily from one of two major sources: either a local source or a regional source. Sabah has seen an upsurge in low to moderate seismic activity in recent years as a result of the fault activities. Between 1900 and lately, magnitudes ranging from MW 2.9 to 6.0 were recorded. While big magnitude earthquakes are relatively uncommon, the area has previously been struck by disastrous earthquakes. Fortunately, the region is demarcated by active Quaternary fault networks. As a result, the area’s seismicity is calculated using line sources corresponding to these faults. Two major fault systems are suspected of being the cause of such activity: the Mensaban fault zone and the Mesilou fault zone, as well as several additional nearby faults. This article explains the process for doing a probabilistic seismic hazard analysis (PSHA) while taking into consideration the peak ground acceleration (PGA) on bedrock in the Ranau region for a 10% and 2% chance of exceedance. The PGA estimate values for Ranau are between 0.08g to 0.16g for PGA 10%, while for PGA 2% was between 0.15g to 0.28g. The PGA value is divided into the following five earthquake hazard classes based on a quarterly geostatistical analysis method. These are “very low,” “low,” “medium,” “high,” and “very high” classes. In general, this quarterly classification is a good way to see how much local seismic activity there is, based on the PGA value. Which can be seen in 10% probability, 19.88 percent of the study area was in “very low,” 20.19 percent was low, 19.98 percent medium, and 19.92 percent high class. 2% probability, it was found that 19.74 percent of the total area was very low class, 20.06 percent low class, 19.79 percent middle class, and 19.82 percent high class. Only 20.6 percent of the area was “very high”.

Variasi spasial dan temporal nilai-b pada gempa bumi di wilayah Sulawesi Tengah, Gorontalo, dan sekitarnya menggunakan metode robust fitting

This study discusses variation in seismic and tectonic modeled by a Gutenberg-Richter relationship for earthquakes in the Central Sulawesi, Gorontalo, and surrounding areas using the Robust Fitting Method (RFM) with the weight function of Tukey’s bisquare. The declustering process on earthquake data is carried out using the Reasenberg equation. The values for both parameters are analyzed spatially and temporally. In the spatial analysis, the research area is divided into 43 grids. In the temporal analysis, the research area is divided into zone A and zone B. The data grouping is done using a sliding time window method, i.e., grouping 50 earthquake catalogs with 5 overlapping events. The results according to spatial analysis show that the b-values range from 0.38 – 1.19. Areas with low b-values (0.38 – 0.7) occur around the Palu-Koro Fault, i.e., Palu city, Malacca strait, and to Toli-Toli, and also in the northern region of Gorontalo, i.e., the subduction plate of the Sulawesi Sea. Meanwhile, high b-values (0.71 – 1.19) are in the Tomini Bay area which is an area with frequent occurrence of earthquakes but has the small potential to generate large-scale earthquakes. The results of the temporal b-value estimation in zones A and B range between values of 0.38 - 1.25. The b-values appear to decrease before the occurrence of major earthquakes in 1996 and 2018 in zone A. The b-values decreased before the occurrence of major earthquakes in 1990, 1991, 2000, and 2008 in zone B. However, the b-values cannot be used as a precursor before the big earthquake in 1997.
 Keywords: Tukey’s bisquare, Reasenberg equation, Gutenberg-Richter relationship, sliding time window, Robust Fitting Method. MSC2020: 86A15

Book Review: Review of Earthquake Children: Building Resilience from the Ruins of Tokyo, 2020

“I was at school when the big earthquake struck. I got a terrible shock. Before long it turned into a great fire. We went to the Honjo Clothing Depot to escape the fires. My father got burned and died. My big sister was crushed by people and died. Now it is just me, my mother, my other big sister, and my big brother.” A testimony from Kimura Sayoko, a first-grader in the 1923 Great Kantω Earthquake. ( The Big Earthquake 1924 [p. 66 in Earthquake Children]).

Comparative Analysis of the Wounded in Patients and Deaths in a Hospital Following the Three Major Earthquakes in Western China.

The purpose of this study was to analyze the injury characteristics of patients and therapeutic strategies for patients injured in the last three big earthquakes in China, so as to provide a reference for the improvement of emergency plans for earthquakes. The analysis was based on the data provided by the Mianyang Central Hospital (MCH) from May 12th, 2008 to September 26th, 2017. Microsoft EXCEL software was used for data input, and SPSS was used for statistical analysis. A total of 1,390 earthquake-related patients were hospitalized in MCH. Most patients were admitted to the hospital within the first 2 weeks after the earthquake. The main causes for seismic injuries involved hit/strike by objects or building collapse /burying. Extremity fractures accounted for most injuries, especially 3 days after an earthquake. But soft tissue injuries cannot be neglected. Most earthquake patients were mainly treated by means of surgery and the majority were related to orthopedics. We found that different areas, population, and religions needed a tailored approach to the rescue effort. Therefore, the earthquake magnitude scale has a significant influence on mechanisms, types and severity of the injury of patients injured in earthquakes, as well as their timely transfer, management, and prognosis. Traumatic injuries are very common and thereby various surgical procedures especially orthopedic and neurosurgery are the domain of treatment modalities. Disaster preparedness and combined surgical team effort need to be focused on to reduce both mortality and morbidity.

Re-use of concrete/brick debris emerged from big earthquake in recycled concrete with zero residues

Nepal’s big earthquake in 2015 caused the accumulation of about 18.85 million tons of debris. Nepal Government was failed to address the management of demolished concrete/brick debris. The samples of concrete/brick debris were collected from the demolished building site and were disintegrated into coarse aggregates, fine aggregates, and powder materials. The recycled coarse aggregate was properly washed to eliminate the contaminants. Recycled bricks were used in both oven-dry (OD) and saturated surface dry (SSD) conditions. The use of 100% recycled coarse aggregate increased the slump from 3 cm to 5 cm and 28-day compressive strength was increased by 4.5%. The slump value of 20% SSD brick aggregate was increased to 5 cm with the decrease of compressive strength by 15% respectively. However, the use of 20% OD aggregate did not affect the slump value. It increased the strength by 10.1%. The use of recycled fine aggregate decreased the slump but the powder increased it. 10% and 20% recycled powder decreased the strength by 24.2% and 27.3% respectively. It was 7.3% and 8.9% respectively for the case of recycled fine aggregates. It is recommended to use the proposed recycling system to manage all remaining concrete/brick debris to make the cities clean and smart.

Die Verkleidung der Cheopspyramide fiel durch Menschenhand, nicht durch das Erdbeben von 1303!

Summary The recently published opinion that the casing stones of the pyramid of Khufu had collapsed after the big earthquake of 1303 AD cannot be maintained.

Microseismicity along Xiaojiang Fault Zone (Southeastern Tibetan Plateau) and the characterization of interseismic fault behavior

The Xiaojiang Fault (XJF) Zone locates in the southeastern of Tibetan Plateau and defines the boundary between the South China and Sichuan-Yunnan blocks. Historical large earthquakes were hosted on the XJF, though its seismic hazard in the near future is under debate. In this study, we utilize portable broad-band seismic network to unravel the microseismic activities along XJF, and to further investigate the fault structures and their properties. Adopting PALM, a newly developed earthquake detection algorithm, we obtained ~13,000 relocated events. The micro-seismicity reveals widespread off-fault structures showing conjugate geometry, while the major faults present low seismicity. The fault branches conjugate to the main-fault present intensive microseismicity, which hosts repeating events and presents high b-value. Regional GPS stations reflect slips are mostly concentrated along the XJF, while the slip rate on off-fault branches correlates with seismic activities on these structures. Combining with other recent seismological and magnetotellurics evidences, we suggest a low strength on these off-fault structures, which may partially release tectonic stress loading and serve as a barrier for future big earthquakes. On the XJF, the microseismic events are clustered on the fault junctions with low b-value. A special set of clusters between 25°N to 25.5°N show an along-strike variation of depth from 10 to 25-km, imaging the boundary between creeping and locked fault portions. We revisit the seismic hazard problem of XJF, and conclude that XJF is at the late stage of inter-seismic period.

Nonlinear Statistical Features of the Seismicity in the Subduction Zone of Tehuantepec Isthmus, Southern México.

After the M8.2 main-shock occurred on 7 September 2017 at the Isthmus of Tehuantepec, Mexico, the spatial distribution of seismicity has showed a clear clusterization of earthquakes along the collision region of the Tehuantepec Transform/Ridge with the Middle America Trench off Chiapas. Furthermore, nowadays, the temporal rate of occurrence in the number of earthquakes has also showed a pronounced increase. On the basis of this behavior, we studied the sequence of magnitudes of the earthquakes which occurred within the Isthmus of Tehuantepec in southern Mexico from 2010 to 2020. Since big earthquakes are considered as a phase transition, after the M8.2 main-shock, one must expect changes in the Tehuantepec ridge dynamics, which can be observed considering that the b-value in the Gutenberg–Richter law, has also showed changes in time. The goal of this paper is to characterize the behavior of the seismic activity by using the Gutenberg–Richter law, multifractal detrended fluctuation analysis, visibility graph and nowcasting method. Those methods have showed important parameters in order to assess risk, the multifractality and connectivity. Our findings indicate, first that b-value shows a dependency on time, which is clearly described by our analyses based on nowcasting method, multifractality and visibility graph.

Literature Study on Seismic Analysis of Multi-Storey RC Frame with Different Types of Foundation

In the process of building earthquake-resistant structures and/or retrofitting vulnerable existing structures, seismic analysis is a method for estimating structural reaction. The problem is tough in principle. Because the structural response to big earthquakes is dynamic, nonlinear, and random. In structural engineering, all three features are exceptional, as most problems are (or can be effectively approximated as) static, linear, and predictable. Many existing RCC buildings in seismic zones are inadequate to withstand earthquakes due to rapid urbanization and the development of a high number of multi-story buildings. And also since different foundation types are adopted based on different structural, soil requirement, it is important to analyze the response of structure with different foundation types.

Big Earthquake Again−Reconsideration of “Disaster Prevention of Earthquake”−

Big Earthquake Again−Reconsideration of “Disaster Prevention of Earthquake”−

Estimating the Geological Strength Index (GSI) in Regional Seismic‐Landslide Zonation Using the Empirical Regression Model

The assessment of the strength parameters of geological formations in regional scale which encounters thousands of slopes is a complicated approach and time consuming and needs huge field work. This issue is an important research topic concerning the regional seismic‐landslide susceptibility analysis or hazard zonation. An empirical regression model was presented to estimate the Geological Strength Index (GSI) with an implication on geological quadrangle of Gorgan region at Alborz mountains range (north of Iran). Two main sets of data were applied in this study: (1) geomorphological data including the slope height, aspect, and distance from faults and distance from thrusts and (2) the physical and mechanical properties of rocks including the unit weight, uniaxial compressive strength (σci), and the petrographic constant (mί) of intact rock. The first group was extracted from a 1 : 100,000 digital geologic map and 10 m digital elevation model (DEM) and the second group was obtained from the Hoek–Brown failure criterion recommended tables. Linear regression equations were generated applying data collected from 294 studied stations using SPSS software. The regression equation predicted GSI in terms of (1) the distance from faults, (2) the distance from thrusts, and (3) the uniaxial compressive strength (σci). The equation had an R2 value of 0.739 and thus fit well to the data. The new method in its present state was recommended for the estimation of the GSI values in regional scale conditions for the assessment of landslide susceptibility and hazard mapping or post events landslide occurrence prediction in the case of probable big earthquakes in Alborz area that is required for emergency responses. The results indicated that the estimation error was about ±30 while the average error was within +5 and −5 and average error percentage was about 3%.

Advances in seismic fluid geochemistry and its application in earthquake forecasing

<p indent="0mm">Earthquakes are one of the most serious natural disasters of the world, with huge potential to cause serious injury and damage to humans and society. Earthquake forecasting, however, still remains a worldwide unsolved problem. The generation and occurrence of an earthquake—Accompanied by material migration, energy transmission and abrupt changes of underground conditions—Can result in the migration and evolution of geochemical elements and isotopes in natural fluids. Active fault zones are not only earthquake-prone areas but also deep fluid overflow channels. The geochemical characteristics of fluids in active faults act as good indicators for tectonic and seismic activities due to their high sensitivities to the changes of stress, temperature and permeability in the crust. The spatial and temporal variations of fluids in the active fault zones are closely related to the deep geological process and as well as the type, scale, and state of the active faults. On the contrary, the state change of an active fault can continue to affect the evolution and migration process of the deep fluids. The close relationship between fluid geochemistry and active faults makes fluid geochemistry not only an important role in earthquake forecasting but also an effective means to explain the changes of materials and conditions that take place during an earthquake. Before the occurrence of an earthquake, the stress and strain can lead to complex changes of chemical elements and isotopes in subsurface water, gas, soil and/or other media, that is, seismic fluid geochemistry anomalies. Therefore, in active fault zones or seismically active areas, monitoring the fluid geochemistry in these surface media and effectively identifying anomalies related to earthquakes have been identified as promising methods for earthquake forecasting. In recent years, seismic fluid geochemistry has been widely used to forecast earthquakes around the world due to its comparatively low costs and the advantages of its timeliness, simplicity, and convenience. Furthermore, with the accumulation of observation data, improved data processing methods and summaries of earthquake cases, more and more fluid geochemistry anomalies are being detected before the occurrence of earthquakes, particularly that of big earthquakes. As a result of the early detection of geochemistry anomalies, some earthquakes have even been successfully predicted. In addition, new analytical techniques play a more significant role in studies of the mechanism of earthquake precursors and seismic physical processes. However, most earthquake predictions are currently based on phenomenon correspondence and/or empirical statistics, and the lack of research on the genetic mechanism of seismic fluid geochemistry anomalies leads to difficulties in the further application of this method. As such, there remains significant room for improvement for the construction of a prediction model based on seismic fluid geochemistry. In this paper, the recent research progress of seismic fluid geochemistry in the field of earthquake forecasting is summarised and combined with our research results and insights to provide guidance for future works in earthquake forecasting methods.

Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox

The 2010-11 Canterbury Earthquake Sequence inflicted seismic losses worth more than $40B, which is about 25% of the GDP of New Zealand (as per 2011 data). More than 80% of these losses were insured, which comprised of more than $10B covered by the Earthquake Commission (a New Zealand crown entity providing insurance to residential property owners) and more than $22B (comprising of roughly equal split between domestic and commercial claims) by private insurers [1]. The scale of financial impact has been perceived to be disproportionately large given the building regulatory regime in New Zealand is relatively stringent and the earthquakes and aftershocks were of moderate magnitude. As it is well known that some of the major faults spread in the Wellington region and the subduction boundary passing through the centre of New Zealand can generate much bigger earthquakes (upwards of magnitude 8), people are left pondering whether New Zealand is able to cope with the financial impact of larger earthquakes. This fearful realisation gradually led to people being dissatisfied with merely life-safe buildings and demanding more resilient buildings that meet the objectives of performance based design; i.e. suffer less damage, incur less loss, and can remain functional after earthquakes.&#x0D; In light of the extensive building damage resulting in high financial loss in recent earthquakes, practicing engineers and researchers in New Zealand have been advocating for revising the current design approach to improve performance of new structures and infrastructure in future earthquakes [2-5]. As a result, large proportion of buildings constructed in the last decade (including those built to replace earthquake-damaged buildings) have shied away from the traditional damage-friendly ductile structural systems and instead adopted one of the new and emerging structural systems claimed to be “low-damage”. In many cases, the adopted structural systems are not covered by existing design standards and are approved as alternate solutions through expert peer review. The “low-damage” attribute of most structural systems has been validated by component (or sub-assembly) level experimental tests, but their interactions with other building components and implications of their use in buildings have not been rigorously scrutinised. Hence, the rushed adoption of some of these systems in buildings can surprise the engineering community in future earthquakes with mismatch between the expected and real performances of the buildings; akin to what New Zealand engineering fraternity is currently going through due to realisation of poor seismic performance of precast hollow-core flooring system that has been widely used in New Zealand buildings without rigorous scrutiny.&#x0D; One such “low-damage” structural system is precast post-tensioned rocking frames with supplemental energy dissipaters. This paper summarises the development of this structural system, critically reviews the literature reporting the seismic performance of this system, and qualitatively evaluates system-level implications of its use in buildings. This paper is intended to better inform engineers of the likely seismic performance of buildings with this structural system so that they can optimise its benefits by giving due consideration to its effect on other building components.

Unmanned Aerial Vehicle (UAV) and Photogrammetric Technic for 3D Tsunamis Safety Modeling in Cilacap, Indonesia

Three-dimensional (3D) modeling of tsunami events is intended to promote tsunami safety. However, the developed 3D modeling methods based on Computational Fluid Dynamics and photorealistic particle visualization have some weaknesses, such as not being similar to the original environment, not measuring the wave’s end point, and low image accuracy. The method for 3D modeling of tsunamis that results from this research can fulfil those weaknesses because it has advantages, such as being able to predict the end point of waves, similar to the original environment, and the height and area of inundation. In addition, the method produces more detailed and sharper spatial data. Modeling in this research is conducted using Agisoft Metashape Professional software to a produce 3D orthomosaic from pictures taken with Unmanned Aerial Vehicle (UAV) technique or drone (photogrammetry), and 3ds max software is used for wave simulation. We take a sample of an area in Cilacap, Indonesia that was impacted by the 2006 southwest coast tsunamis and may be vulnerable to future big megathrust earthquakes and tsunamis. The results could be used to provide several benefits, such as the creation of evacuation routes and the determination of appropriate locations for building shelters.

Are The Teachers Prepared For The Expected Big Earthquake?

Deprem, oldukça yıkıcı maddi ve manevi sonuçları olan doğal afetlerdendir. Türkiye’nin yer aldığı bölge sismik hareketler açısından önemli deprem bölgelerinden birinde yer almaktadır. Türkiye’nin deprem riski taşıyan bölgelerinden biri de Doğu Anadolu Fay Sistemi (DAFS) üzerinde olan Gölbaşı – Türkoğlu fay parçasıdır. Söz konusu fay parçasında meydana gelen son büyük deprem (8 şiddetinde) 1795 yılında meydana gelmiş ve yapılan araştırmalar neticesinde bölgede 7.7 şiddetinde deprem beklendiği anlaşılmaktadır. Bu amaçla; bahsedilen fay parçasının üzerinde yer alan Kahramanmaraş/Türkoğlu’nda görevli olan öğretmenlerin “Sağlık İnanç Modeli” kapsamında, beklenen bu büyük depreme bireysel hazırlık düzeyleriyle ilgili çalışma yapılmıştır. 300 öğretmenle nicel araştırma yöntemlerinden tarama ve ilişkisel araştırma modeli kullanılarak yürütülen bu araştırma, demografik değişkenler olan yaş, cinsiyet, medeni durum, çocuk sayısı, yaşanılan yer, afet deneyimi, 24 Ocak Elazığ Depremi’ni yaşama durumu, deprem çantası ve afet eğitimi durumları açılarından incelenmiştir. Elde edilen bulgulara göre öğretmenlerin depreme karşı bireysel hazırlık düzeylerinin ortadan yüksek düzeyde olduğu anlaşılmıştır. Ayrıca yaşı daha büyük, evli, çocuk ve ev sahibi, afet ve Elazığ Depremi deneyimine sahip, deprem çantası hazırlayan ve afet eğitimi almış olanların depreme bireysel hazırlık düzeylerinin daha yüksek olduğu anlaşılmıştır. Bu nedenle öğretmenlerde bireysel hazırlıkların yüksek düzeye çıkarılması yönünde çok yönlü çalışmalar ve planlamalar yapılması önerilmektedir.

Stochastic Simulation of Strong Ground Motions From Two M &gt; 5 Uttarakhand Earthquakes

Many studies based on the geodetic data and statistical analysis of seismicity have pointed out that sufficient amount of stress accumulated in the Himalayan plate boundary may host a big earthquake. Consequently, high seismic activities and infrastructural developments in the major cities around Himalayan regions are always of major concern. The ground motion parameter estimation plays a vital role in the near real time evaluation of potentially damaged areas and helps in mitigating the seismic hazard. Therefore, keeping in mind the importance of estimation of ground motion parameters, we targeted two moderate-size earthquakes that occurred recently within a gap of 10 months in Uttarakhand region with M &amp;gt; 5.0 on 06/02/2017 and 06/12/2017. The ground motions are simulated by adopting a stochastic modeling technique. The source is assumed as ω−2, a circular point source (Brune’s model). The average value of reported anelastic attenuation from various studies, the quality factor, Qs= 130.4*(f0.996), and stress drop values obtained through iterative procedure are considered for simulations. The stochastic spectra are generated between 0.1 and 10 Hz of frequency range. The site effect is also estimated by using the H/V method in the same frequency range. The synthetic spectra are compared with the observed Fourier amplitude spectra obtained from the recorded waveform data and converted back to the time histories. The stochastic time histories are compared with the observed waveforms and discussed in terms of amplitude (PGA). The simulated and observed response spectra at different structural periods are also discussed. The mismatch between the observed and simulated PGA values along with the GMPE existing for shallow crustal earthquakes is also discussed in the present work.