Mid Niigata Prefecture Earthquake Research Articles

Assessment of earthquake-triggered landslide susceptibility considering coseismic ground deformation

The distance to the surface rupture zone has been commonly regarded as an important influencing factor in the evaluation of earthquake-triggered landslide susceptibility. However, the obvious surface rupture zones usually do not occur in some buried-fault earthquake cases, which means information about the distance to the surface rupture is lacking. In this study, a new influencing factor named coseismic ground deformation was added to remedy this shortcoming. The Mid-Niigata prefecture earthquake was regarded as the study case. To select a more suitable model for generating the landslide susceptibility map, three commonly used models named logistic regression (LR), artificial neural network (ANN), and support vector machine (SVM) were also conducted to assess landslide susceptibility. The performances of these three models were evaluated with the receiver operating characteristic curve. The calculated results showed that the ANN model has the highest area under the curve (AUC) value of 0.82. As the earthquake triggered more landslides in the epicenter area, which makes it more prone to landslides in further earthquakes, the susceptibility analysis at two different mapping scales (the whole study area and the epicenter area) was also applied.

Bayesian-based joint determination of earthquake hypocentres and 1-D velocity structures divided by a structural boundary

SUMMARY We propose a Bayesian approach for jointly determining the locations of earthquake hypocentres and velocity structures in a region divided by a structural boundary, such as a fault zone. To accommodate the Markov chain Monte Carlo (MCMC) method in a region containing lateral velocity contrast, we incorporated a data-driven station clustering scheme when estimating earthquake hypocentre locations, a 1-D velocity model assigned to each cluster and station corrections for traveltimes. The proposed method realizes the clustering of stations reflecting velocity structures beneath the station network in the framework of the MCMC method. We verified the performances of the proposed method using numerical experiments with different distributions of earthquake hypocentres relative to the structural boundary. The results demonstrated that the proposed method reconstructed earthquake hypocentre locations and velocity structures involving lateral contrast robustly to earthquake distributions. Additionally, the number of 1-D velocity models (the number of station clusters) was optimized by comparing resultant posterior probability proportional to distances between the observed and theoretical traveltimes. We also applied the proposed method to estimate the earthquake hypocentre locations and velocity structures around the source area of the 2004 Mid-Niigata prefecture earthquake, Japan, to examine the applicability of the proposed method to real observation data. The stations were divided into east and west clusters, coinciding with the lateral velocity variation related to the geological setting. Therefore, the proposed method accurately determines earthquake hypocentres in a region divided by a structural boundary without any knowledge regarding the geological structure.

Characteristics of landslide distribution after the Mid-Niigata Prefecture Earthquake in 2004

Characteristics of landslide distribution after the Mid-Niigata Prefecture Earthquake in 2004

Identification of shear strength and seismic coefficient by back analyzing surficial slides in the 2004 Mid-Niigata prefecture earthquake

Sliding of natural and artificial slopes generally occurs during or following strong earthquakes. Such sliding is greatly affected by a combination of geological conditions and earthquake loading. Earthquake-induced landslides often cause more damage to infrastructure and human lives than the earthquake itself. Pseudo-static analysis is widely implemented as one of several design methods used in engineering practice to assess the seismic stability of natural and artificial slopes. However, the most important issue of pseudo-static analysis is to select the most appropriate method for measuring seismic coefficient. In order to investigate this, back analysis was conducted for surficial slides subjected to strong ground motion during the 2004 Mid-Niigata prefecture earthquake in Japan. This paper surveyed the stochastic properties of earthquake-induced surficial slides and clearly showed that the obtained results were applicable to back analysis of shear strength and seismic coefficient. In back analysis, soil properties such as soil strength and density and sliding depth were assumed as random variables owing to their uncertainties. Seismic coefficient is also assumed to be a random variable and varies with distance from the epicenter fault line. The analysis of 4504 recorded surficial slides clearly shows a unique relationship of landslide occurrence ratio with slope angle and distance from the epicenter fault line. This study’s results enhance the calculation of the shear strength of weathered soil covering slopes and the horizontal seismic coefficient through back analysis procedure. By considering possible stochastic properties of variables, some case studies were implemented in the back analysis.

Co-seismic stress changes and damage to tunnels in the 23 October 2004 Mid-Niigata Prefecture earthquake

Recent near-field earthquakes accompanied by large soil deformations have been clouding the notion that mountain tunnels would be safe places during earthquakes. One of the recent eye-openers was the damage to railway tunnels in the 2004 Mid-Niigata Prefecture earthquake. Changes in stresses in the interior of a half-space of stratified sedimentary rocks, as a representative of the earthquake-hit region, are obtained using the authors’ previous works on co-seismic deformations of this region to study the damage mechanism of deeply embedded railway tunnels. The values of square root of the second invariant of the stress deviator tensor, [Formula: see text], and the first invariant of Cauchy stress tensor, [Formula: see text], are compared with the reported damages along the entire stretch of selected tunnels and a very good correlation is observed between the peak values of [Formula: see text] and the damaged sections of the tunnels. A yield surface is defined as the boundary between clusters of points for damaged and undamaged tunnel sections in the scatter diagram of [Formula: see text] and [Formula: see text]. This yield surface and rock–soil deformability can be used to examine the margin of safety of both existing and new tunnels as well as for hazard zonation in a given scenario earthquake.

O-219 新潟平野の液状化現象 : 新潟県中越地震と新潟地震の事例から(24.環境地質,口頭およびポスター発表,一般講演)

O-219 新潟平野の液状化現象 : 新潟県中越地震と新潟地震の事例から(24.環境地質,口頭およびポスター発表,一般講演)

新潟県中越地震における長岡市悠久山地域の段丘および沖積低地の震害要因 ―谷状凹地と水路による被害規制―( 新潟県中越地震の被害と地質)

新潟県中越地震における長岡市悠久山地域の段丘および沖積低地の震害要因 ―谷状凹地と水路による被害規制―( 新潟県中越地震の被害と地質)

更新世末期の陥没盆地 ―魚沼丘陵北部・田麦山陥没盆地―( 新潟県中越地震の被害と地質)

更新世末期の陥没盆地 ―魚沼丘陵北部・田麦山陥没盆地―( 新潟県中越地震の被害と地質)

特集「新潟県中越地震の被害と地質」を刊行するにあたって( 新潟県中越地震の被害と地質)

特集「新潟県中越地震の被害と地質」を刊行するにあたって( 新潟県中越地震の被害と地質)

Regional landslide susceptibility following the Mid NIIGATA prefecture earthquake in 2004 with NEWMARK’S sliding block analysis

This study proposes a calculation method for regional earthquake-induced landslide susceptibility that applies the permanent seismic displacement calculated using Newmark’s sliding block analysis with estimated vertical and horizontal seismic motions. The proposed method takes into account the direction of slope failure based on the specified slope azimuth. The study results reveal the importance of predominant slope failure direction using a simple infinite slope model subjected to earthquakes. The target area for the earthquake-induced landslide susceptibility analysis constituted a region of more than 2000 km2 surrounding the epicenter of the Mid Niigata prefecture earthquake in 2004. An earthquake-induced landslide susceptibility map was created based on the proposed method with a specific combination of friction angle and cohesion, and the resulting data were compared to the landslide inventory map produced from aerial photographs following the Mid Niigata prefecture earthquake in 2004. To create the susceptibility map, geomaterial cohesion values for the slope were back-calculated to satisfy the minimum safety factor in the static state. This study also proposes a calculation method for the prediction rate and determines the back-calculated strength parameters of geomaterials. The proposed regional landslide susceptibility map will be useful for understanding potential slope failure locations and magnitude of damage, as well as for planning field investigation and preventing secondary disasters immediately after earthquakes.

Spatial distribution of landslides induced by the 2004 Mid-Niigata prefecture earthquake, Japan

On October 23, 2004, an earthquake with a moment magnitude of 6.8 occurred in the Chuetsu area of Niigata prefecture in Japan. This earthquake is known as the 2004 Mid-Niigata prefecture earthquake; the event was followed by severe aftershocks and caused many types of landslides such as surficial slides, shallow slides, and deep slides. A large number of landslides occurred in the upland village of Yamakoshi, destroying the entire village; in addition, a huge number of houses collapsed in Kawaguchi town. This study investigates the correlations between each type of landslide and the bedding plane orientation and dip, and other geomorphologic conditions. The landslide occurrence ratio (LOR) is used as an index to determine the correlation between the 2004 Mid-Niigata prefecture earthquake-induced landslides and the slope angle, slope aspect, rock type, and bedding plane orientation and dip. This work also proposes a methodology to determine the geometric alignment between the topography and the orientation of geological bedding planes. The method provides an efficient means of estimating the topography/bedding plane relationship over large areas.

Ground motion estimation for the elevated bridges of the Kyushu Shinkansen derailment caused by the foreshock of the 2016 Kumamoto earthquake based on the site-effect substitution method

An earthquake of JMA magnitude 6.5 (first event) hit Kumamoto Prefecture, Japan, at 21:26 JST, April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (second event) hit Kumamoto and Oita Prefectures at 01:46 JST, April 16, 2016. An out-of-service Kyushu Shinkansen train carrying no passengers traveling on elevated bridges was derailed by the first event. This was the third derailment caused by an earthquake in the history of the Japanese Shinkansen, after one caused by the 2004 Mid-Niigata Prefecture Earthquake and another triggered by the 2011 Tohoku Earthquake. To analyze the mechanism of this third derailment, it is crucial to evaluate the strong ground motion at the derailment site with high accuracy. For this study, temporary earthquake observations were first carried out at a location near the bridge site; these observations were conducted because although the JMA Kumamoto Station site and the derailment site are closely located, the ground response characteristics at these sites differ. Next, empirical site amplification and phase effects were evaluated based on the obtained observation records. Finally, seismic waveforms during the first event at the bridge site of interest were estimated based on the site-effect substitution method. The resulting estimated acceleration and velocity waveforms for the derailment site include much larger amplitudes than the waveforms recorded at the JMA Kumamoto and MLIT Kumamoto station sites. The reliability of these estimates is confirmed by the finding that the same methods reproduce strong ground motions at the MLIT Kumamoto Station site accurately. These estimated ground motions will be useful for reasonable safety assessment of anti-derailment devices on elevated railway bridges.

Layered internal structure and breaching risk assessment of the Higashi-Takezawa landslide dam in Niigata, Japan

The internal structure and geotechnical properties of landslide dams have rarely been examined in detail, although they largely control the longevity and potential failure mechanisms of the dams. During the 2004 Mid-Niigata Prefecture earthquake, thousands of landslides were triggered and many landslide dams were formed in the Imo River basin. Among these landslides dams, the biggest one that occurred in the Higashi-Takezawa district threatened both the upstream and downstream areas. Emergency and eventual permanent countermeasures were successfully performed to mitigate the hazards presented by the dam. The preserved landslide dam provides a good field study area for improving understanding of the formation and stability of similar features. To characterize its internal structure and to provide more reliable information for stability analysis, we used a multiple-channel surface-wave technique and microtremor array measurements to survey the dam's S-wave velocity (Vs) profile. Our results show that the integrated use of these methods is an effective approach for determining the S-wave velocity structure of landslide dams, irrespective of the mountainous environment in which they typically occur. The Vs profile suggests that the displaced landslide materials had been little disturbed during movement, although movement was rapid and over a long distance. We also discuss herein the landsliding mechanism and assess the breaching risk of the landslide dam due to overtopping.

Large-Scale Koi Breedersʼ Efforts around Hilly and Mountainous Area after the Mid-Niigata Prefecture Earthquake in 2004

Large-Scale Koi Breedersʼ Efforts around Hilly and Mountainous Area after the Mid-Niigata Prefecture Earthquake in 2004

Self-affinities analysis of fault-related folding

The Mid-Niigata Prefecture Earthquake did not rupture the earth's surface and occurred along a fault hidden well under folded terrain. In order to evaluate the seismic activity of such hidden earthquakes beneath fault-related folds, a new method to analyze self-affinities is introduced. Based on this analysis, the geometry of a fold is shown to be self-affine and can be variously scaled in different directions. The size and temporal properties, b-value in Gutenberg - Richter's law and p-value in the modified Omori's law, express aftershock activity. Then, from the analyzed data of the folds, we estimate the b-value and p-value of the hidden earthquake under the fault-related folds. These estimated b-values and p-values are concordant with seismologically obtained ones in the aftershock sequence of the Mid-Niigata Prefecture Earthquake.

Evidence of a hidden landslide slip surface beneath a mountain hamlet

Earthquake-triggered landslides are some of the most destructive natural disasters. Although remote detection of landslides is economic and efficient, it may miss the more subtle signs of hidden landslides. The Kizawa Tunnel and facilities in its vicinity were severely damaged in the 2004 mid-Niigata Prefecture earthquake. After investigation of the most prominent cracks, the damage was attributed to the slip along a hidden weakness plane. Evidence supporting this argument is summarized in this paper. However, the extent of the shear plane is not limited to the interior of the northern part of the tunnel. The dislocation observed in the two wells to the south of the Kizawa Tunnel together with other findings from previous studies indicates that Kizawa hamlet lies on the southern extension of the same shear plane. Taking account of the presence of flat sedimentary structures, the shear plane may extend in all directions. The authors also surveyed other signs of damage along the perimeter where the shear plane intersects the ground surface. The geological and geomorphological features of the hidden landslide are discussed. Reactivation of interlayer sliding is a threat to the local residents, and thus more attention should be paid to monitoring the movement of the slope to avoid devastating damages.

Series: Physicians and disaster medical care: Third stage, Management and education for disaster medicine: disaster medical coordination system (1). Mid Niigata Prefecture earthquake in 2004 & Niigataken Chuetsu-oki earthquake in 2007

Series: Physicians and disaster medical care: Third stage, Management and education for disaster medicine: disaster medical coordination system (1). Mid Niigata Prefecture earthquake in 2004 & Niigataken Chuetsu-oki earthquake in 2007

既存地すべり地形との比較による新潟県中越地震による地すべりの規模と移動範囲の特徴

既存地すべり地形との比較による新潟県中越地震による地すべりの規模と移動範囲の特徴

2004年新潟県中越地震による地すべり・斜面崩壊と東山丘陵の地形発達との関係

The 2004 Mid-Niigata Prefecture earthquake induced many landslides in the Higashiyama Hills, central Japan. The epicenter of the earthquake was near the axis of an active fold called the Higashiyama anticlinorium, but the density of earthquake-triggered landslides was relatively low around the anticlinorium's axis. In contrast, landslide density was high on both limbs of the anticlinorium. This study analyzes the factors responsible for this difference in earthquake-induced landslide density from the viewpoints of landform development and microgeomorphology. The folding of the Higashiyama anticlinorium since the latest early Pleistocene has been uplifting the Higashiyama Hills; the 2004 earthquake was one event of this crustal movement. Microgeomorphological classification using a 2-m-mesh DEM around the middle fork of the Imo River indicates that landslide density is high on the steep slopes of the river valley, which are dissected by down-cutting of the Imo River and its tributaries. In contrast, the area around the axis of the Higashiyama anticlinorium is characterized by deep-seated landslide geomorphology, without dissecting valleys, and relatively low relief. As a result, earthquake-induced landslides are sparse there. These differences in slope geomorphology reflect geomorphic processes in actively uplifting hills and mountains with active folding. This viewpoint is applicable to estimating the potential for co-seismic landsliding.

Role of regional development activity in mountain village after Mid Niigata Prefecture Earthquake in 2004

Role of regional development activity in mountain village after Mid Niigata Prefecture Earthquake in 2004