Hokkaido Eastern Iburi Earthquake Research Articles

4-② 地震前後の衛星SAR画像解析とレーザ地形データ差分解析による造成地周辺の地盤変位

4-② 地震前後の衛星SAR画像解析とレーザ地形データ差分解析による造成地周辺の地盤変位

Landslides induced by the 2018 Hokkaido Eastern Iburi Earthquake

Landslides induced by the 2018 Hokkaido Eastern Iburi Earthquake

Extracting Persons in Need of Evacuation Support Based on Information on Daily Life during the Disaster: Case Study of Initial Responses by Tsurui Village, Hokkaido, to the Hokkaido Eastern Iburi Earthquake

Extracting Persons in Need of Evacuation Support Based on Information on Daily Life during the Disaster: Case Study of Initial Responses by Tsurui Village, Hokkaido, to the Hokkaido Eastern Iburi Earthquake

Response to Complex Disaster Centered on the 2018 Hokkaido Eastern Iburi Earthquake

Response to Complex Disaster Centered on the 2018 Hokkaido Eastern Iburi Earthquake

Investigation and mechanism analysis of disasters under Hokkaido Eastern Iburi earthquake

An Mw6.6 earthquake occurred at 3a.m. on September 6, 2018, in the eastern part of Iburi, Hokkaido. This earthquake killed 41 people, caused a series of service interruptions in Sapporo city. Soil liquefaction and approximately 6000 landslides were triggered. A field investigation was conducted on liquefaction and typical landslides during September 18 to 24, 2018. The liquefaction disaster exhibited soil flow, subgrade collapse, uneven settlement, earthquake subsidence, and deformation of buildings. After investigation of typical landslides, it was found that owing to the continuous heavy rainfall and typhoon, the surface soil had a high-water content. A layered loam of approximately 2 m below ground surface developed into a weak surface. Based on the analysis of sliding morphology, the landslides were classified into translational earth slides and earth flow. To clarify the mechanism of regional landslides, the stability and permanent displacement of slopes considering effect of continuous heavy rainfall and seismic motion was analyzed. Limit equilibrium analysis was applied based on the pseudo-static method. Then Newmark displacement calculation was conducted based on the seismic acceleration record. The distribution range of analysis results showed agreement with actual landslides disasters. The results verified the contribution of continuous rainfall and strong motion to the failure of regional slopes.

Groundwater Anomaly Related to CCS-CO2 Injection and the 2018 Hokkaido Eastern Iburi Earthquake in Japan

Carbon capture and storage (CCS) is considered a key technology for reducing CO2emissions into the atmosphere. Nonetheless, there are concerns that if injected CO2migrates in the crust, it may trigger slip of pre-existing faults. In order to test if this is the case, covariations of carbon, hydrogen, and oxygen isotopes of groundwater measured from Uenae well, southern Hokkaido, Japan are reported. This well is located 13 km away from the injection point of the Tomakomai CCS project and 21 km from the epicenter of September 6th, 2018 Hokkaido Eastern Iburi earthquake (M 6.7). Carbon isotope composition was constant from June 2015 to February 2018, and decreased significantly from April 2018 to November 2019, while total dissolved inorganic carbon (TDIC) content showed a corresponding increase. A decrease in radiocarbon andδ13C values suggests aquifer contamination by anthropogenic carbon, which could possibly be attributable to CCS-injected CO2. If such is the case, the CO2enriched fluid may have initially migrated through permeable channels, blocking the fluid flow from the source region, increasing pore pressure in the focal region and triggering the natural earthquake where the brittle crust is already critically stressed.

平成30年度北海道胆振東部地震における建築・建築設備被害に関する報告 その1 戸建住宅の被害

平成30年度北海道胆振東部地震における建築・建築設備被害に関する報告 その1 戸建住宅の被害

平成30年度北海道胆振東部地震における建築・建築設備被害に関する報告 その２ 集合住宅に与えた影響

平成30年度北海道胆振東部地震における建築・建築設備被害に関する報告 その２ 集合住宅に与えた影響

Tourism Stakeholder Perspective for Disaster-Management Process and Resilience: The Case of the 2018 Hokkaido Eastern Iburi Earthquake in Japan

The 2018 Eastern Iburi Hokkaido earthquake in Japan caused infrastructural damage and tourism disruption within a natural-hazard-prone country. This research advances the theoretical foundation and development of natural disaster management through a series of in-depth interviews with the local tourism stakeholders on the investigation of how the role of tourism across the pre-to-post earthquake period is considered by the stakeholders. These local tourism stakeholders have performed or expected a range of actions related to the disaster-management process and contributed to destination resilience. The qualitative analysis discovers, firstly, the multi-functionality of tourism resources, spaces, and industries for disaster preparation; secondly, the evacuation and emergency arrangements during the prodromal and emergency phases; and moreover, more possibilities of restoring the affected destination to a state of long-term (re)development during the post-disaster phases. Information and communication barriers are the major difficulties to be tackled for disaster preparedness. Product creation, image improvement, local knowledge enrichment, and, more importantly, people-to-people and people-to-place connections all contribute to the result of sustainable tourism development. From the destination resilience perspective, collaboration is the key determinant of an improved Hokkaido region. This factor could integrate stakeholders through shared local values, experiences, and memories of disaster risk communication and strategies for preparedness.

Evacuation awareness and behavior in the event of a tsunami in an aging society: An experience from the 2018 Hokkaido Eastern Iburi earthquake

Of all natural disasters, the dual catastrophe of earthquake and tsunami is one of the most dangerous, due to the suddenness and unpredictability of these events. Hokkaido, the biggest island situated to the north of Japan, has a lower frequency of earthquakes and tsunamis compared to other parts of the country. Nevertheless, the occurrence of the Hokkaido Eastern Iburi earthquake in September 2018 raised important awareness in the local community of the tsunami threat. In this study we aim to examine the behavior in response to the potential of a tsunami in the city of Muroran, a community with an aging population. Our results highlight that the increase in age, homeownership, and living alone negatively impact the act and intention of evacuation. By contrast, collecting information, dwelling location, perceived seismic intensity, reserving tools and food, and post-earthquake action positively influences evacuation behavior. Remarkably, grasping news and age have the strongest impacts, while house location, shock intensity, preparedness of emergency tools, and post-earthquake actions respectively, have a medium effect on people's behavior. The lowest influence variables are homeownership status, food stocking, and living alone. These results not only contribute to the disaster prevention theory, but also support policymakers in risk management planning, as well as improve the safety of the community and environment.

How the large-scale blackout following the 2018 Hokkaido Eastern Iburi earthquake impacted adolescents\u2019 sleep patterns

A blackout on the island of Hokkaido occurred following a massive earthquake on September 6, 2018. This study analyzed the sleep pattern data of junior high school students on the night of the blackout in comparison to a normal night. Data were collected from 52 junior high school students from a school away from the earthquake’s epicenter but within the blackout area. Although the students normally slept less than 8 h per night, they slept for nine and a half hours during the blackout night. The duration during the blackout corresponded to the ideal sleep duration recommended by the NSF and AASM.

Landslide detection in mountainous forest areas using polarimetry and interferometric coherence

The cloud-free, wide-swath, day-and-night observation capability of synthetic aperture radar (SAR) has an important role in rapid landslide monitoring to reduce economic and human losses. Although interferometric SAR (InSAR) analysis is widely used to monitor landslides, it is difficult to use that for rapid landslide detection in mountainous forest areas because of significant decorrelation. We combined polarimetric SAR (PolSAR), InSAR, and digital elevation model (DEM) analysis to detect landslides induced by the July 2017 Heavy Rain in Northern Kyushu and by the 2018 Hokkaido Eastern Iburi Earthquake. This study uses fully polarimetric L-band SAR data from the ALOS-2 PALSAR-2 satellite. The simple thresholding of polarimetric parameters (alpha angle and Pauli components) was found to be effective. The study also found that supervised classification using PolSAR, InSAR, and DEM parameters provided high accuracy, although this method should be used carefully because its accuracy depends on the geological characteristics of the training data. Regarding polarimetric configurations, at least dual-polarimetry (e.g., HH and HV) is required for landslide detection, and quad-polarimetry is recommended. These results demonstrate the feasibility of rapid landslide detection using L-band SAR images.

Geological features of landslides caused by the 2018 Hokkaido Eastern Iburi Earthquake in Japan

Abstract Before dawn on 6 September 2018, a powerful earthquake with a Japan Meteorological Agency magnitude ( M j ) of 6.7 hit central Hokkaido, causing more than 6000 landslides. As human damage, 36 of the 44 fatalities from the earthquake were from earthslides in Atsuma Town. Most slope movements were shallow earthslides of mantle-bedded tephra and soil layers, but some were deep rockslides involving basement rocks such as shale and mudstone of Miocene. Although the shallow earthslides were easily distinguishable in photos from satellites or airplane, the rockslides were more difficult to identify owing to their vegetation. Based on the quick interpretation of a high-resolution (0.5 m horizontal resolution) shaded relief map made from digital elevation model data by airborne laser survey and supplemental field surveys, we effectively identified 259 rockslides (196 certain ones and 63 possible ones) in Atsuma and Mukawa towns under newly invented identification criteria based on the scarp depth and positional relation between scarp and ridge topography. It was revealed that most rockslides were distributed within 10 km from the epicentre, while earthslides were distributed until 20 km north of the epicentre, and they seemed to be controlled by the thickness of mantle-bedded tephra and the soil layer. We also identified many traces of past rockslides and earthslides. The results show the possibilities for effective measurement of slope by clarifying the landslide distribution both this earthquake and past ones using high-resolution digital elevation model data.

Dynamic rupture simulation of 2018, Hokkaido Eastern Iburi earthquake: role of non-planar geometry

The 2018, Hokkaido Eastern Iburi, Japan, earthquake is an event characterized by complexity of the rupture process and slip pattern, which may involve both reverse and strike-slip motion depending on the locations on the fault surface. We perform dynamic rupture simulations based on simple physical laws, conditions for stressing and fault friction, and the non-planar fault geometry constrained by the aftershock observation. The complex fault geometry is numerically treated by the boundary integral equation method accelerated by the fast domain portioning method. The fault geometry is characterized primarily by the combination of six fault planes. As a result, we are able to explain several observed features of the event, including the spatial variation of the final fault slip and rupture velocity, which are inferred from the kinematic slip inversion. We also succeed in refining the constraint of the regional stress field in the focal area based on the simulation. Our results show that the overall patterns of the complex rupture event can be reproduced by a relatively simple model of the regional stress and the fault friction, if the geometrical complexity of the fault is properly taken into account.

Message from the Winner

I would like to express my sincere appreciation for the honor of receiving this prestigious award. The award has been presented to me for the “Special Issue on NIED Frontier Researches on Science and Technology for Disaster Risk Reduction and Resilience 2017” of JDR Vol.12 No.5, for which I was the guest editor. I heard that this special issue has been the most downloaded over the past three years. NIED, to which I belong, is an institute that deals with natural disasters comprehensively. Since 2016, we have been working to become a “core organization for innovation in disaster resilience science and technology” as a new seven-year plan. Japan is a country prone to disasters, with many large-scale natural disasters occurring every year. Recent examples would be the 2016 Kumamoto Earthquake, 2017 Nasu Avalanche, Northern-Kyushu Heavy Rain, 2018 Eruption of Mt. Kusatsu-Shirane, Western-Japan Heavy Rain, Hokkaido Eastern Iburi Earthquake, and 2019 Typhoon #19. We should collect “intelligence” related to natural disasters in multiple fields to reduce our disaster risk and improve our resilience. The Special Issue is a compilation of research results from individual fields. I am elated that the first special issue of NIED has gained such attention. NIED will continue to conduct research across multiple fields. We hope that NIED’s activities will lead to collaboration with many people and that the integration of intelligence will improve disaster resilience in Japan and all over the world.

Controlling role of Ta-d pumice on the coseismic landslides triggered by 2018 Hokkaido Eastern Iburi Earthquake

The 2018 Hokkaido Eastern Iburi Earthquake triggered massive landslides in the pyroclastic fall deposits. Most of them are shallow debris slides. Based on the field reconnaissance, the shallow debris slides were further categorized into three types: steep translational sliding, gentle translational sliding, and mobilization of V-shaped convergent sliding masses. The three types of shallow landslides were investigated in depth through longitudinal sections, vertical stratigraphic sections, and in situ hardness tests. All three types of shallow landslides were found to initiate from the liquefied failure of the weak Ta-d pumice layer and further evolve to the overall mobilization of the superimposed pyroclastic fall deposits along the liquefied sliding zone. To testify the controlling role and to study the shear behavior as well as the anti-liquefaction strength of the weak Ta-d pumice layer, a series of laboratory tests (basic physical tests and triaxial tests) were conducted on the soils around the sliding zone. The test results indicate that the medium sandy Ta-d pumice MS and the fragile Ta-d pumice CS have lower shear resistance and anti-liquefaction strength than other layers and they can be easily liquefied under intense ground motion. One paleosol layer underlying the Ta-d pumice shows low permeability and enables weathering and soil erosion of the Ta-d pumice, resulting in the widespread existence of the fragile and medium sandy pumice layers in Ta-d. In addition, the positive relationship between coseismic landslide density and Ta-d pumice thickness demonstrates the controlling role of the Ta-d on Iburi landslide occurrence from a macro perspective.

Turbidity Water Occurrence in a Basin after The 2018 Hokkaido Eastern Iburi Earthquake and Consideration of a Management Method of Intake for Agriculture to Prevent an Effect of Turbidity Water Intake

Turbidity Water Occurrence in a Basin after The 2018 Hokkaido Eastern Iburi Earthquake and Consideration of a Management Method of Intake for Agriculture to Prevent an Effect of Turbidity Water Intake

Landslides which Occurred in Atsuma Area of Iburi Region due to 2018 Hokkaido Eastern Iburi Earthquake

Landslides which Occurred in Atsuma Area of Iburi Region due to 2018 Hokkaido Eastern Iburi Earthquake

Various internal structures of upheaval zone around terminal part of landslide : A case of tephra slide induced by 2018 Hokkaido Eastern Iburi Earthquake

Various internal structures of upheaval zone around terminal part of landslide : A case of tephra slide induced by 2018 Hokkaido Eastern Iburi Earthquake

Reforestation in landslides caused by the 2018 Hokkaido Eastern Iburi Earthquake

Reforestation in landslides caused by the 2018 Hokkaido Eastern Iburi Earthquake