Seismic Intensity Distribution Research Articles

Kinematic deformation and intensity assessment of the 2021 Maduo MS7.4 earthquake in Qinghai revealed by high-frequency GNSS

Rapid acquisition of the kinematic deformation field and seismic intensity distribution of large earthquakes is crucial for postseismic emergency rescue, disaster assessment, and future seismic risk research. The advancement of GNSS observation and data processing makes it play an important role in this field, especially the high-frequency GNSS. We used the differential positioning method to calculate the 1 HZ GNSS data from 98 sites within 1000 km of the MS7.4 Maduo earthquake epicenter. The kinematic deformation field and the distribution of the seismic intensity by using the peak ground velocity derived from displacement waveforms were obtained. The results show that: 1) Horizontal coseismic response deformation levels ranging from 25 mm to 301 mm can be observed within a 1000 km radius from the epicenter. Coseismic response deformation on the east and west sides shows bilateral asymmetry, which markedly differs from the symmetry presented by surface rupture. 2) The seismic intensity obtained through high-frequency GNSS and field investigations exhibits good consistency of the scope and orientation in the high seismic intensity area, although the former is generally slightly smaller than the latter. 3) There may exist obstacles on the eastern side of the seismogenic fault. The Maduo earthquake induced a certain tectonic stress loading effect on the western Kunlun Pass-Jiangcuo fault (KPJF) and Maqin-Maqu segment, resulting in higher seismic risk in the future.

Multifractal analysis of temporal and spatial characteristics of earthquakes in Eurasian seismic belt

Abstract Seismic activity has complexity and randomness, and its temporal and spatial distribution has complexity, stage, level, and inheritance. The study of the temporal and spatial distribution characteristics of seismic activity is of great significance to the understanding of the law of seismic activity, such as the law that the time series of seismicity in the seismic belt is consistent with the complexity of geographical structure, the prediction of seismic risk, and other research related to earthquake. This article selects the seismic data catalog of the whole Eurasian seismic belt as the research object. Based on the characteristics of the seismic geological environment and tectonic environment characteristics, the multifractal analysis method is used for the seismic data of the seismic activity directory. The results show that the seismic activity of seismic zones has obvious multifractal structure of complex in time series and spatial scales, which can well reveal the seismic characteristics of seismic activity in time and space. In terms of time series, the study area D ∞ {D}_{{\rm{\infty }}} decreases significantly with time and energy before the occurrence of a large earthquake, and the time series of seismic activity in the study area is highly complex and highly correlated with the geological structure. Spatially, the spatial distribution of seismic intensity in the study area is infinite and sparse, showing the characteristics of infinite clustering. Therefore, it can reveal the basic rule of seismic activity effectively and lay a certain theoretical foundation for earthquake prevention and control in this seismic zone.

Development Pattern of Toppling Deformation Slopes in Western China

Controlled by regional geological background, and affected by human activity and weathering, toppling deformation slopes occur in different regions in China. Based on statistics about domestic toppling deformation slopes and their distribution, the regional geological susceptibility zonation area of toppling deformation slopes was determined. Firstly, a regional geological susceptibility evaluation was conducted according to these toppling deformation slopes, choosing landform, stratigraphic age, seismic intensity and tectonic stress distribution, and the study area was divided into very low, low, medium, high and very high susceptibility areas. Secondly, a geographic position susceptibility evaluation was conducted aimed at different sections of typical rivers in western China and the toppling deformation slopes related to them, and the study area was divided into upstream, midstream and downstream of 11 rivers that were respectively classified into very low, low, high and very high susceptibility areas. Thirdly, based on the results, associations between the toppling deformation factors (lithology, slope height, elevation, horizontal depth and vertical depth) and the distribution of deformation slopes were revealed. Finally, the development regularity was analyzed comprehensively. The results show that the toppling deformation slopes of hydropower projects are more developed in Sichuan, Qinghai and Yunnan provinces of China. With regard to regional geography, besides the Yellow River, both the Lancang River and the Yalong River flow through areas with toppling deformation that are classified as highly susceptible geological zones in all levels. The results of this study can be used as references for site selection plans in hydropower projects.

東京低地の埋没谷形状と地盤震動特性：上野-小岩測線での検討結果

To better understand how ground motion in the Tokyo Lowland is affected by the geological conditions in the shallow subsurface, we analyzed borehole logs and conducted microtremor observations along the Ueno-Koiwa survey line, which crosses the buried valley beneath the Tokyo Lowland. Remarkable peaks in the H/V spectra at ~1 Hz were found in the area of the lower buried terrace (buried flat surface 2), whereas the peaks at ~1 Hz are small in the area of the buried valley bottom with the thickest valley-filling post-Last Glacial Maximum (LGM) deposits. The sharp peaks around buried terrace 2 are generated by the large contrast in the physical properties of the soft, muddy post-LGM deposits and the underlying gravel bed, which suggests larger ground-motion amplification during an earthquake. The variation of the ground motion characteristics along the survey line obtained by microtremor observation is consistent with the distribution of seismic intensity during the 1923 Kanto Earthquake. It is, therefore, important to consider not only the thickness and physical properties of the post-LGM deposits during seismic hazard assessment, but also the total geological composition, including the Pleistocene strata below the post-LGM deposits.

Focal mechanism of Luding M 6.8 earthquake, September 2022 and analysis of the loading role of the tectonic stress on the seismogenic fault

To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion approach to calculate the focal mechanism solution of the M6.8 Luding earthquake that occurred on September 5, 2022. We have also studied the loading effect of tectonic stress on the Luding earthquake fault based on the stress field data for the research area. The results indicate that this earthquake was a strike-slip type, the nodal plane I: strike 167°, dip Angle 78°, slip Angle 2°; Nodal plane Ⅱ: strike 77°, dip Angle 88°, slip Angle 168°. The two fault planes’ instability coefficients of the Luding earthquake are examined considering the region’s background stress field’s condition. The nodal plane I in the Moho circle is discovered to practically coincide with the Coulomb failure line and the tangent point of the Moho circle, indicating that this nodal plane has a high instability coefficient compared to the nodal plane II. The conclusion is that the nodal plane I has a higher likelihood of being the seismogenic fault plane, which is congruent with the seismogenic fault plane suggested by the aftershock distribution, the earthquake radiation energy distribution of a single station, and seismic intensity distribution. The Luding earthquake’s focal mechanism is highly like the theoretical focal mechanism of the fault situated at the location where the Coulomb failure line intersects the Mohr circle, demonstrating that background stress is what caused the earthquake. The substantial fault instability and similarity between the solved and theoretical focal mechanisms make it easier to comprehend the loading effect of tectonic stress on the Luding earthquake fault.

High-resolution calibration of seismically-induced lacustrine deposits with historical earthquake data in the Eastern Alps (Carinthia, Austria)

Lake sediments are increasingly used to reconstruct recurrence intervals of large earthquakes - a prerequisite for the establishment of accurate seismic hazard models - because they can record strong seismic shaking as mass-transport deposits (MTDs), turbidites or sediment deformations and often reach back several thousands of years. To derive quantitative information on paleo-earthquake size, the sedimentary imprints need to be thoroughly calibrated with independent information on seismic shaking strength. A few calibration studies proposed scaling relationships between the shaking strength of historical earthquakes and the type and size of lacustrine sedimentary imprints. Due to incomprehensive lacustrine mapping or an insufficient record of documented earthquakes, however, rigorous testing of these scaling relationships is lacking. Here, we study the sedimentary infill of the past ∼800 years in Wörthersee and Millstättersee, two large lakes in the Eastern Alps (Carinthia, Austria). These lakes have experienced five well-documented historical earthquakes with local seismic intensities ranging from V – IX (EMS-98 scale). We trace the sedimentary signatures (MTDs and turbidites) of these earthquakes based on a vast dataset of multibeam bathymetry, reflection seismic profiles and numerous precisely dated sediment cores. Seismic intensities as low as V½ are recorded as turbidites originating from deltaic slopes, while hemipelagic slopes can fail from intensities of VI onwards. In Wörthersee, earthquake-recording thresholds are highly dependent on the specific core locations due to local variations in slope characteristics (composition, length, and gradient) and transport distance to the core site. This highlights the potential for establishing multi-threshold paleoseismic records based on multiple coring sites in a single basin. In both lakes, exponential size-scaling relationships are inferred between seismic intensity and i) number or volume of mass-transport deposits and ii) the cumulative thickness of turbidites. Moreover, the relative turbidite presence increases linearly with seismic intensity, confirming the results from a previous study in Chilean lakes. Application of the obtained size-scaling relationships on the first major earthquake documented for Austria (1201 CE) suggests a magnitude of ∼6.4 and an epicentre close to Millstätter See. This demonstrates that lake paleoseismology is a powerful tool to obtain quantitative information on the seismic intensity distribution of paleo-earthquakes.

Application of the Modified PLUM Method to a Dense Seismic Intensity Network of a Local Government in Japan: A Case Study on Tottori Prefecture

An application of the PLUM (Propagation of Local Undamped Motion) method to real-time seismic intensity distribution from a dense seismic intensity network maintained by a local government in Japan is demonstrated. The JMA (Japan Meteorological Agency) has employed the PLUM method from March 2018 as a supplement to the traditional EEW (Earthquake Early Warning) which requires hypocenter determination. A dense observation network is desirable for upgrading accuracy and immediateness of EEW including the PLUM method. Seismic intensity meters in Tottori Prefecture, Japan, are suitable for the purpose because they have been improved to broadcast packets with peak ground acceleration and JMA seismic intensity at every 1 s. Also, 34 seismic intensity meters are installed in the target area while only six observation sites are used for the EEW by the JMA. The packet data are received at Tottori University, and the modified PLUM method considers wave propagation with damping from not only the observation points but also all evaluating grid points at a 1 km mesh. Additionally, P-wave amplitudes in preliminary tremors are also introduced to estimate seismic intensities from an empirical relationship. Applying the methodology to past earthquake data, more detailed and rapid evaluations of seismic intensity distribution are achieved. We expect the system will be utilized for earthquake disaster mitigation measures of local governments.

Research on application of focal mechanism and site conditions in judgment of Hebei earthquake influence field

The determination of seismic influence field in post-earthquake work, a quickly gived reasonable map of seismic intensity distribution, was an important basis for emergency rescue after the earthquake and was important for the government to understand the disaster situation, deploy work and estimate the disaster loss. In this paper, the isoseismal maps of moderate strong earthquakes in Hebei Province were collected and sorted out, it was compared with the theoretical isotherm map generated by the regional earthquake intensity attenuation relationship based on the focal mechanism solution. The results show that, with the increase of magnitude, the similarity was higher between the theoretical isoseismal map and the actual isoseismal map in the high intensity area （≥Ⅶ）, the theoretical isoseismal map was calculated by the attenuation relationship of seismic intensity with focal mechanism solution. In addition, according to the spatial variation of aftershock frequency within 24 hours after the earthquake, the theoretical isoseismal line in the polar region is modified, which is more consistent with the actual isoseismal line. That is to say, the theoretical calculated intensity is closer to the actual investigation intensity value. Finally, the grid of Hebei area was divided, and the bedrock PGA of the earthquake case on each grid center point was calculated according to the attenuation relationship of ground motion. Then, the site category attributes were extracted, considered site amplification factor, and the conversion of bedrock PGA to surface PGA was completed. The surface PGA was converted into intensity and compared with the actual earthquake isoseismal map. The results show that the similarity between the seismic influence field calculated by considering the site amplification effect and the actual isoseismal line was very high in the high intensity area, and the similarity is higher than the intensity attenuation relation method based on the focal mechanism solution.

Seismic Intensity Distribution of the 1914 Sakurajima Earthquake in Kagoshima City, Japan

Seismic Intensity Distribution of the 1914 Sakurajima Earthquake in Kagoshima City, Japan

Deep Learning Model for Spatial Interpolation of Real-Time Seismic Intensity

Abstract Spatial distribution of seismic intensity plays an important role in emergency response during and immediately after an earthquake. In this study, we propose a deep learning model to predict the seismic intensity based on only the observation records at the seismic stations in a surrounding area. The deep learning model is trained using the observation records at both the input and target stations, and no geological information is used. Once the model is developed, for example, using the data from a temporal seismic array, the model can spatially interpolate the seismic intensity from the sparse layout of the seismic stations. The model consists of long short-term memory cells, which are well-established neural network components for time series analysis. We used observed seismograms in 1996 through 2019 at the Kyoshin Network (K-NET) and Kiban–Kyoshin Network (KiK-net) stations located in the northeastern part of Japan. In our deep learning model, approximately 85% of validation data is successfully classified into seismic intensity scales, which is better than adopting either the maximum or weighted average of the input data. We also apply the deep learning model to earthquake early warning (EEW). The model can predict the seismic intensity accurately and provides a long warning time. We concluded that our approach is a possible future solution for increasing the accuracy of EEW.

Relationship between detailed seismic intensity distribution and averaged S wave velocities by a conventional microtremor array survey - Based on questionnaire survey of seismic intensity in Ofunato City, Iwate Prefecture, for the 2003 off-Miyagi earthquake (Mj7.1) -

岩手県大船渡市の振動特性を明らかにするため，2003年5月26日に発生した宮城県沖地震（Mj 7.0）のアンケート震度調査を行った。震度の算出には太田ら（1998）の改訂版を用いた。大船渡市の小学校14校，中学校8校の生徒の両親に3,387枚のアンケートを配布した。アンケートから推定された震度は，震度の分布を明確にするために250m四方のメッシュで平均した。アンケート調査のための個人間の違いを避けるために，アンケートの数が3つ以上の有効メッシュを分析に使用した。大船渡市の有効メッシュ数は212であった。メッシュ震度は6.4～4.1の範囲で分布し，大船渡市の平均は5.1であった。大船渡市の平野部にあたる中心部では震度が大きく，周辺では震度が小さいことが判明した。2003年宮城県沖地震の強震動は振動特性が地下の地質構造に依存することを示した。

Multihazard Mapping of Banepa and Panauti Municipalities

A combination of rough topography, steep slopes, active tectonic and seismic process and intense impact of monsoon rain has made the fragile environment of Nepal vulnerable to a variety of natural hazards. Most frequent hazards are floods, landslides, epidemics, fires, earthquake and other hydro-meteorological disasters, causing heavy loss of human lives as well as economic loss including housing and infrastructures (MDRIP, 2009). Hence, hazard assessments are the need of the hour. They help district and regional decision makers, policy makers and development agencies prepare disaster risk reduction plans. The chosen study area was Banepa and Panauti municipality. Separate hazard assessments have been performed for four hazards, namely, earthquake, flood, landslide and industrial hazards.Earthquake hazard zone maps have been made following the Probabilistic Seismic Hazard Assessment (PSHA) approach for 500 year return period to produce seismic intensity distribution maps in the form of Modified Mercalli Intensity (MMI) maps using Trifunac and Brady formula. Flood inundation maps have been made using HEC-RAS and HEC-GeoRAS extension for ArcGIS for return periods of 2, 10 and 500 of Chandeswori and Punyamata rivers. Landslide hazard susceptibility map has been made using the Stability Index Mapping (SINMAP) extension for ArcGIS that uses an infinite-slope equation accurate for debris flows. Industrial hazard maps that depict the vicinity that falls within various ranges of danger in the event of different industrial hazards like fire, Vapor Cloud Explosion (VCE) and Boiling Liquid Expanding Vapor Explosion (BLEVE) have been prepared as well. Finally, a composite multi hazard map has been prepared by combining all the four hazards.Nepalese Journal on Geoinformatics -13, 2014, Page: 25-31

Characteristics of Seismic Intensity Distribution in the Vicinity of Focal Area Along the Southern Hida Mountain Range, Central Japan

Characteristics of Seismic Intensity Distribution in the Vicinity of Focal Area Along the Southern Hida Mountain Range, Central Japan

地域減災設計の実現に向けた震度曝露人口適合想定地震の選定手法

In Japan, each prefecture selects some scenario earthquakes, and uses them for making a regional disaster prevention plan. They select scenarios which cause the largest loss, but the scenarios' event probabilities are not considered. It is too conservative and uneconomical to plan a regional disaster prevention for a scenario which has a very low event probability. “Hazard-consistent scenario earthquake” was proposed as a method of selecting scenario earthquakes based on probability. But this method is not appropriate to be used for planning a regional disaster plan because this method is based on a hazard analysis at only one point. So, for example, this method can't distinguish a case where a seismic intensity of 5 upper is observed in only small area from a case where it is observed in almost all area in a region. “Risk-consistent scenario earthquake” (Ishiskawa & Okumura, 2001) can avoid this problem. But in a previous study, each risk curve of prefectures is calculated based on an assumption that all houses have been built at a prefectural capital. In this study, “PEX-consistent scenario earthquakes” is proposed. This is a new method of probabilistic scenario earthquakes based on the relationship between population exposure to seismic intensity (PEX) and its exceedance probability (P-PEX relation). Population distribution is thought to be positively correlated with various social wealth, so PEX represents simply an effect of earthquakes. The Proposal method consists of three steps. First, calculating P-PEX relation and each seismic zones’ contribution for it. Second, determining the seismic zone corresponding to the target risk level. Third, determining a seismic intensity distribution of the background earthquakes corresponding to the level. Following results are obtained in this study. 1) In almost all prefectures, background earthquakes are included in scenario earthquakes corresponding to the specific risk level. But only about 20 prefectures consider background earthquakes in their loss estimations. 2) In Tokyo, the seismic intensity distribution of intraplate earthquake of Philippine sea plate corresponding to 100 yr. return period is lower than the scenario of Tokyo prefectural government, and the distribution corresponding to the 2500 yr. return period is very much higher than it.

Profile and Management of Musculoskeletal Injuries Associated With the Lushan Earthquake in 2013.

On April 20, 2013, a 7.0-magnitude earthquake hit Lushan County, Ya'an City, Sichuan Province in southwest China. West China Hospital of Sichuan University, the largest and best hospital in Sichuan Province, is located in the city of Chengdu-about 100 km from the epicenter-and provided medical treatment to a total of 400 seismic patients. In this article, we retrospectively investigated 199 patients with musculoskeletal injuries who were treated in the Department of Orthopedics. Based on the seismic intensity distribution map, injury-occurring locations were divided into 5 grade-related areas: IX, VIII, VII, VI, and ≤V grade-area. The characteristics of seismic injuries were analyzed according to the geographic distribution of victims. We found that the constituent ratio of injury causes significantly differed in different earthquake areas according to the seismic intensity. (Disaster Med Public Health Preparedness. 2018; 12: 408-410).

The 1748 Montesa (southeast Spain) earthquake — A singular event

The Montesa earthquake of 23 March 1748 in southeast Spain caused heavy damage and was felt over a wide area. It occurred in a region considered of low seismic hazard where few large earthquakes have happened. The abundant contemporary documentation about the damage caused by the earthquake, especially to the castle of Montesa and the city of Játiva, allows a re-evaluation of the seismic intensity distribution giving a maximum intensity I=IX (EMS-1998). The focal parameters are estimated as: origin time 6h 30m local time, epicentre 39.00°N 0.64°W, and magnitude 6. The spatial distribution of ground acceleration derived from intensity values is modelled on a very shallow bilateral rupture of 10km length with strike 60°, dip 45°, and rake 90°. This source orientation agrees with the faults present in the area.

1945年1月13日三河地震の広域震度分布の再評価とその特徴

1945年1月13日三河地震の広域震度分布の再評価とその特徴

1944年東南海地震の広域震度分布の再評価と被害の特徴

1944年東南海地震の広域震度分布の再評価と被害の特徴

Very exceptional cases of VLF/LF ionospheric perturbations for deep oceanic earthquakes offshore the Japan island

It is so far believed that ionospheric perturbations as detected by subionospheric VLF/LF (very low frequency/low frequency) propagation, are generated above and around the earthquake (EQ) epicenter. This paper presents very rare cases, which are in complete contrast to the above fact. We have found that in extremely rare cases when EQs happened (i) in the Pacific Ocean or (ii) offshore the Soya cape (Hokkaido) both with very large depths (300–400km), corresponding ionospheric perturbations take place far away from the EQ epicenter and above the regions with considerable seismic intensity at the time of each EQ. Two EQs happened in the Torishima area of Izu islands (magnitude ∼7 and depth ∼400km), and corresponding seismic intensity was observed in the Tokyo and Ibaraki districts. Our VLF data have indicated that the ionospheric perturbation takes place over such regions with high seismic intensity. Another group is two EQs (magnitude ∼5) offshore the Soya cape of Hokkaido, and the spatial distribution of seismic intensity at the time of each EQ is just around Aomori prefecture. VLF data have indicated the ionospheric perturbations taken place over the same Aomori area, which is in complete coincidence with the spatial distribution of seismic intensity. As a conclusion, these exceptional examples are, in principle, very similar to the concept of ‘selectivity’ (or sensitive zone) of geoelectric measurement by the Greek group, and we try to interpret these cases in the context of lithosphere-atmosphere–ionosphere coupling.

New characteristics of intensity assessment of Sichuan Lushan “4.20” M s7.0 earthquake

The post-earthquake rapid accurate assessment of macro influence of seismic ground motion is of significance for earthquake emergency relief, post-earthquake reconstruction and scientific research. The seismic intensity distribution map released by the Lushan earthquake field team of the China Earthquake Administration (CEA) five days after the strong earthquake (M7.0) occurred in Lushan County of Sichuan Ya’an City at 8:02 on April 20, 2013 provides a scientific basis for emergency relief, economic loss assessment and post-earthquake reconstruction. In this paper, the means for blind estimation of macroscopic intensity, field estimation of macro intensity, and review of intensity, as well as corresponding problems are discussed in detail, and the intensity distribution characteristics of the Lushan “4.20” M7.0 earthquake and its influential factors are analyzed, providing a reference for future seismic intensity assessments.