3D numerical modeling of landslide-generated tsunamis around a conical island

This paper presents numerical computations of tsunamis generated by landslides falling along the flank of a conical island. The model used is the fully three-dimensional commercial code FLOW-3D, based on the VOF technique for the treatment of the free surface. The model results are compared against available experimental data that allow validation of the model, evaluation of its accuracy, and estimation of the computational costs. The main conclusion of this research is that the model is applicable at reasonable costs for a few accurate simulations that may be used for preparing precomputed inundation maps of coasts prone to the risk of tsunamis inundation.     

Uncovering unnoticed small-scale tsunamis: field survey in Lombok,Indonesia, following the 2018 earthquakes

Natural Hazards - In 2018, Lombok island, Indonesia, was hit by a series of destructive earthquakes that caused thousands of casualties and widespread material damage. In response to those events,...     

Earthquakes and tsunamis in a region of diapiric folding

New Zealand earthquakes rarely cause significant tsunamis. In 1947 two tsunamis reaching a height of about 10 m were associated with earthquakes of less than magnitude 6. Their records have the predominantly low-frequency character of the tsunami-generating shocks on the inner margin of the Japan Trench, but they originated beneath a shallow coastal platform, and not close to the Hikurangi Trench. The platform consists of weak folded sediments penetrated by diapiric intrusions from which large quantities of mud and breccia have been explosively expelled from time to time. The mechanical behaviour of this extruded material is believed to be responsible for the character of the shocks, and to provide a mechanism for the generation of tsunamis.     

Tsunami risk reduction for densely populated Southeast Asian cities: analysis of vehicular and pedestrian evacuation for the city of Padang, Indonesia, and assessment of interventions

A major tsunamigenic earthquake is expected in the near future along the coast of West Sumatra Province of Indonesia. In the city of Padang, the arrival time of the tsunami is expected to be ~30 min. Currently, there are approximately 400,000 people in the city living within the potential inundation zone. This study aimed to complement the existing research in appraising possible risk reduction interventions, specifically looking at enabling the timely evacuation of the area. This research, developed in consultation with national and local authorities, emergency planners and NGOs, analysed interventions for tsunami risk reduction in Padang through the development of a pedestrian and vehicular evacuation model and the appraisal of possible solutions to enhance the evacuation rates. Some of the conclusions from this research can be applied to other areas in Southeast Asia where the traffic patterns are similar to those in Padang and where the distance to safety is greater than 4–5 km. For the case of Padang, the results show that pedestrian evacuation is strongly preferable to vehicular evacuation due to the limited road capacity and the high population density. In the present situation, however, 70–80 % of the population in Padang could not evacuate within 30 min, even by foot. Common interventions such as widening roads and building bridges prove to be relatively ineffective in this case due to the large distance that has to be covered in a short time. These interventions would only have a decisive impact if a longer evacuation time was available (more than 60 min). In the case of Padang, the evacuation rate in the first 30 min is strongly dependent on the presence/absence of evacuation shelters, whose effectiveness is limited by the capacity of the structures. Building a few high-capacity and high-resilience structures such as evacuation hills is a more effective and robust evacuation strategy than constructing many small high-raised buildings. Even with evacuation structures, wider roads and bridges, about 20 % of the population would still be unable to reach safety by the time the tsunami arrives. This means about 70,000 people of Padang’s current population, which is rapidly increasing. The building of evacuation shelters may be a viable option for saving lives in the short term, but it is not a sustainable option in the medium to long term. It is therefore also necessary to set up and enforce regulations for land use planning that take into account the tsunami risk and prevent further urban development for the areas that may be affected by a tsunami.     

安宁河流域典型沟谷泥石流危险性评价

冕宁县安宁河流域为地质灾害密集分布区,安宁河断裂穿越于此,构造复杂,冷渍沟在上游左岸发育。在强降雨条件下,该沟就会暴发泥石流,堵塞安宁河流域和掩埋杀叶马村房屋和道路。冷渍沟泥石流具有流域面积小,主沟长度短,沟床纵比降大等特征,为了研究安宁河流域内泥石流的危险性,以冷渍沟为例,分析不同降雨周期下的泥石流暴发强度,模拟泥石流的运动过程并进行危险性评价。模拟的最大流速、最大堆积深度和降雨强度三者结合建立冷渍沟泥石流危险性评价模型。研究结果表明,冷渍沟泥石流危险范围内高危险区域占27%,主要集中在松散固体物质较多的沟道,中危险性区域和低危险区域各占56%和17%,该结论为危险范围内的居民和重点设施的风险管控提供参考。     

Modeling of inundation dynamics on Banda Aceh,Indonesia during the great Sumatra tsunamis December 26, 2004

The tsunami inundation flows on Banda Aceh, Indonesia reached 5 km inland during the December 26, 2004, event and devastated most of the houses, buildings, and infrastructure along the coast and killed more than 167,000 people. The overland flows from the northwest coast and the west coast collided at Lampisang village approximately 3.7 km from Ulee Lheue (northwest coast) and 6.8 km from Lhok Nga (west coast) as reported by survivors. Inundation modeling based on the nonlinear shallow-water wave equations reproduces the inundation pattern and demonstrates a colliding of the overland flows. The model suggests that wave characteristics on the northwest coast of Banda Aceh were different from those on the waves that impacted upon the west coast. The areas, which experienced higher inundation levels, did not always experience greatest overland flow speeds, and the damage areas mostly coincide with the flow speed distribution rather than the runup and inundation depth.     

Middle Jurassic radiolarian chert,Indarung, Padang District,and its implications for the tectonic evolution of western Sumatra,Indonesia

Radiolaria from chert in the Indarung Area belong to the Transhsuum hisuikyoense Zone, indicating an Aalenian, lower Middle Jurassic, age. Carbonate in the area has been dated as Upper Jurassic to Lower Cretaceous from the occurrence of Lovcenipora, and overlying tuff has given a radiometric K/Ar age of 105±3 (Albian, uppermost Lower Cretaceous). The chert and carbonate are probably in tectonic contact, with the chert faulted into the limestone during ENE-directed compression. This comprises one of the best dated occurrences of allochthonous material in Sumatra and confirms the accretion of oceanic material along the Sunda margin during Mid- to Late-Cretaceous times.     

Plate boundary evolution in the Halmahera region,Indonesia

Halmahera is situated in eastern Indonesia at the southwest corner of the Philippine Sea Plate. Active arc-arc collision is in process in the Molucca Sea to the west of Halmahera. New stratigraphic observations from Halmahera link this island and the east Philippines and record the history of subduction of the Molucca Sea lithosphere. The Halmahera Basement Complex and the basement of east Mindanao were part of an arc and forearc of Late Cretaceous-Early Tertiary age and have formed part of a single plate since the Late Eocene-Early Oligocene. There is no evidence that Halmahera formed part of an Oligo-Miocene arc but arc volcanism, associated with eastwards subduction of the Molucca Sea beneath Halmahera, began in the Pliocene and the Pliocene arc is built on a basement of the early Tertiary arc. Arc volcanism ceased briefly during the Pleistocene and the arc shifted westwards after an episode of deformation. The present active arc is built upon deformed rocks of the Pliocene arc. The combination of new stratigraphic information from the Halmahera islands and models of the present-day tectonic structure of the region deduced from seismic and other geophysical studies is used to constrain the tectonic evolution of the region since the Miocene. Diachronous collision at the western edge of the Philippine Sea Plate which began in Mindanao in the Late Miocene impeded the movement of the Philippine Sea Plate and further motion has been achieved by a combination of strike-slip motion along the Philippine Fault, subduction at the Philippine Trench and subduction of the Molucca Sea lithosphere beneath Halmahera.     

Hazard and risk intensity maps for water-bearing units: a case study

Fresh groundwater from intergranular and carbonate aquifers are considered as the valuable resources for domestic, agricultural and industrial water supplies of the Iraqi Kurdistan Region. A comprehensive approach to groundwater protection using the intrinsic vulnerability, hazard and risk intensity mapping was proposed by the European COST Action 620. The current article applied all the components of the above mentioned Pan-European approach to assess the risk harmfulness in the Sulaimani sub-basin by combining hydrogeological parameters using the DRASTIC system and the hazard components by taking the product of the weighted hazard value (H_I), the ranking factor (Q_n) and the reduction factor (R_f). The hazard map was constructed from twenty-six hazard feature types of the point, line and polygon. Their distributions, extents and of harmfulness degrees vary sharply from one place to another. Results of the risk intensity map divided the area into five classes as “no or very low, low, moderate, high and very high” risk zones. Fortunately, the majority of the area of interest is classified as very low to low contamination potential due to the limited impact of hazards as well as low groundwater vulnerabilities. The zones with moderate-risk potentials clustered in industrialized areas.     

低密度地球化学填图在热带雨林区的适用性探索：以印度尼西亚苏门答腊岛巴东明古鲁地区为例

不同尺度地球化学填图能否获得稳定的和可追索的地球化学模式,能否真实反映元素含量背景,是检验填图方法是否可行的重要依据。笔者选择印度尼西亚苏门答腊岛巴东—明古鲁地区热带雨林区为研究对象,对比该区1:100 万（1 个样/100 km2）和1:25 万（1 个样/4 km2）两种不同比例尺的地球化学采样所获得的地球化学数据和异常分布模式,发现二者获得的元素含量背景值和中位数非常接近,所圈定的地球化学省在形态和变化趋势上非常类似,浓集中心的位置几乎完全重合,证明低密度地球化学填图也能获得稳定的和可追溯的地球化学模式,认为该方法在热带雨林区也是适用的。低密度地球化学填图圈出的地球化学省基本涵盖了研究区大的矿床和花岗岩体,真实的反映了研究区元素的分布情况,在这些地球化学省内开展更大比例尺的地球化学填图工作,能进一步圈定局部异常直接找矿,降低企业勘查投资风险。     

Occupational transitions in three coastal villages in Central Java, Indonesia, in the context of sea level rise: a case study

The transition from one system to another as a mechanism of adaptation to an external disturbance is widely discussed in terms of ‘regime shifts’ in resilience research. But occupational transitions by communities due to coastal hazards such as coastal erosion and strong waves have not been studied in depth from a systems perspective. Such a perspective can contribute towards a better understanding of the process and pattern behind transformation among coastal societies. The present case study of coastal occupational communities in Central Java province, Indonesia, includes fishers, brackish pond farmers and labourers. It investigates the historical occupational transitions and the factors that drive them. The study draws on Participatory Rural Appraisal exercises such as historical timeline analysis and participatory discussions along with a socio-economic survey to study the factors and processes that led these communities to transitional pathways. Historical narratives of the community reveal the significance and influence of livelihood capitals such as social, human, financial, physical and natural capital in the transitions. Through the ‘Marble and Cup’ conceptual framework of the systems transitions, the irreversibility of occupational transitions due to the destruction of natural assets is outlined. This depicts a multi-locale and one-dimensional transition to a singular occupational mode (essentially labourers) in the face of a disturbance like sea level rise, necessitating transformation and building of the livelihood capitals across geographical scales.     

Rock burst assessment in multi-seam mining: a case study

To assess rock burst prone zones in the lower seam during multi-seam mining, a rock burst hazard assessment method for use in multi-seam mining was established. According to the observed geological evolution, the feasibility of using upper layer coal mining data to determine the rock burst risk zone of the lower coal seam is explained. Then, we established the energy density risk index (EDRI) and proved that the EDRI more accurately reflected the potential rock burst region than the multi-factor coupling analysis method. Finally, we established the rock burst hazard assessment method for use in multi-seam mining by using the EDRI of the upper coal to divide the rock burst risk zone in the lower coal. From the accuracy and validity analysis of this assessment method, we find that the critical energy induced rock burst, and the damage area of a rock burst in the lower coal seam were all located in the high-risk zone derived from this assessment method. To quantify the effectiveness and practicability of this assessment method, the structural similarity (SSIM) index, from image quality assessment research, was introduced. The SSIM index between predicted-high-risk map and actual high-risk map index was 0.8581, which shows that the established rock burst hazard assessment method in multi-seam mining can be used to predict rock burst risk zones in the lower seam.     

Hydrogeological component assessment for water resources management of semi-arid region: a case study of Gwalior,M.P., India

Groundwater management is of fundamental importance to meet the rapidly expanding urban, industrial and agricultural water requirements in semi-arid areas. To assess the current rate of groundwater withdrawal and possibility of recharge of potential aquifer in the semi-arid regions is essential for water management. The present study aimed to identify potential area for groundwater recharge structure in the Gwalior area based on land use, rainfall variation, hydrological component and statistical analysis. In this work, a stream survival approach was used for the assessment of water channel by using triangulated network and regression analysis to find out the correlation of individual component with reference to water management. Land use/land cover (LULC) map prepared from multispectral satellite images of the study area and used to validate the hydrological component and the results observed through the regression model shows good correlation. Therefore, immediate and effective water management schemes are required for sustainable water resource development and management in the area.     

Drought propagation in the hydrological cycle in a semiarid region: a case study in the Bilate catchment,Ethiopia

Hydrogeology Journal - Drought is a temporal decrease in water availability and occurs in all climatic regions. Droughts propagate through the hydrological cycle, e.g., meteorological drought...     

Basic principles of multi-risk assessment: a case study in Italy

The assessment of the impact of different catastrophic events in a given area requires innovative approaches that allow risks comparison and that account for all the possible risk interactions. In the common practice, the risk evaluation related to different sources is generally done through independent analyses, adopting disparate procedures and time--space resolutions. Such a strategy of risks evaluation has some evident major drawbacks as, for example, it is difficult (if not impossible) to compare the risk of different origins, and the implicit assumption of independence of the risk sources leads to neglect possible interactions among threats and/or cascade effects. The latter may amplify the overall risk, and potentially the multi-risk index could be higher than the simple aggregation of single-risk indexes calculated considering each source as independent from the others. In this paper, we put forward some basic principles for multi-risk assessment, and we consider a real application to Casalnuovo municipality (Southern Italy), in which we face the problem to make different hazards comparable, and we highlight when and how possible interactions among different threats may become important.     

Low-carbon development in the least developed region: a case study of Guangyuan, Sichuan province, southwest China

The Wenchuan earthquake in 2008 has resulted in 50% of Guangyuan city facing recovery from different extents of damages. The massive reconstruction provides a good opportunity for Guangyuan city to response to the National Council??s call for tackling climate change by developing a harmonised and low-carbon economy. However, there are many arguments about the definition of ??low carbon?? and the framework that low-carbon development should follow. Low-carbon development in an economically least developed region such as Guangyuan would provide evidence and contribute to the discussion. The paper employs CO₂ emissions as an environmental indicator in scenario analysis to investigate Guangyuan??s future carbon performance in following the national call of reducing 40% of carbon intensity by 2020 and an alternative low-carbon development path. The results have demonstrated that a ??win?Cwin?? solution can be reached??keeping rapid economic growth while reducing CO₂ emissions, however, only by addressing the ??correct?? determining factors. Technology improvements and production structure changes have been identified as the key determining factors to affect both carbon intensity and CO₂ emissions in the future. The two factors are also interdependent. Governmental policies should give appropriate guideline to address both factors but with strong emphasis on production structure decarbonisation in order to avoid the mistake of ??polluting first and deal with the pollution later?? during the emission-intensive industrialisation processes that many western countries and China??s coastal regions have followed.     

降雨型浅层黄土滑坡危险性评价与区划

黄土高原是我国地质灾害最为发育的地区之一,其中降雨诱发的浅层黄土滑坡又最为典型。以典型黄土地貌区-柳林县为例,应用SINMAP模型,探讨模型在黄土地区的适用性,分析了随着研究区内降雨量的增加,滑坡变形失稳区域的面积变化、分布位置和扩展趋势。研究表明,随着降雨量的增加,滑坡所处位置逐渐由稳定状态向失稳状态发展,位于失稳分区的滑坡数量逐渐增加,说明降雨对该研究区的斜坡稳定性影响较为明显。通过将模拟结果与实际发生的由降雨触发的滑坡灾害进行对比分析,可以得出SINMAP模型在黄土地区,对区域性降雨诱发浅层黄土滑坡稳定性的模拟预测有效,可以用于黄土地区浅层滑坡的稳定性评价研究。     

Hazard risk assessment of landslide-prone sub-Himalayan region by employing geospatial modeling approach

Natural Hazards - Ecological processes such as landslide disaster are primarily impacted by both geological and land use activities happening at different spatiotemporal scale. They specifically...     

GIS-based flood risk assessment in suburban areas: a case study of the Fangshan District,Beijing

Suburban areas have become rapid development zones during China’s current urbanization. Generally, these areas are also regional precipitation centers that are prone to flood disasters. Therefore, it is important to assess the flood risk in suburban areas. In this study, flood risk was defined as the product of hazard and vulnerability based on disaster risk theory. A risk assessment index system was established, and the analytic hierarchy process method was used to determine the index weight. The Fangshan District in Beijing, China, which is an example of a typical suburban area undergoing rapid urbanization, was selected for this study. Six factors were considered in relation to hazard, and three factors were considered for vulnerability. Each indicator was discretized, standardized, weighted, and then combined to obtain the final flood risk map in a geographical information system environment. The results showed that the high and very high risk zones in the Fangshan District were primarily concentrated on Yingfeng Street, Xingcheng Street, Xincheng Street, and Chengguanzhen Street. The comparison to an actual flood disaster suggested that the method was effective and practical. The method can quantitatively reflect the relative magnitude and spatial distribution patterns of flood risk in a region. The method can be applied easily to most suburban areas in China for land use planning and flood risk management.