Geohazard Risk Research Articles

Comparison of landslide inventories from the 1994 Mw 6.8 Arthurs Pass and 2015 Mw 6.0 Wilberforce earthquakes, Canterbury, New Zealand

The 6th January 2015 Mw 6.0 Wilberforce earthquake, 30 km west of Arthurs Pass in the Upper Wilberforce catchment, produced ground shaking of at least 0.22 g, just above the expected threshold for landslide initiation based on previous work. An aerial reconnaissance confirmed that at least 200 landslides occurred within an area of 370 km2. The majority of failures were of moderate volume and occurred on slopes of between 22° and 67°. Approximately 85% of failures occurred within 12 km2 of the earthquake epicentre, although large landslides also occurred outside of this area, at sites where previous landslides had occurred. We compared this inventory with one obtained by a similar method in similar terrain after a Mw 6.8 earthquake in 1994, 20 km southwest of Arthurs Pass. Whilst the 1994 earthquake included a higher proportion of landslides with larger volumes close to the earthquake epicentre, the number of landslides and area that they affected was greater during the Wilberforce earthquake. In addition, the Wilberforce earthquake triggered its second largest landslide at a substantial distance (25 km) from the epicentre, in an area of moderate shaking. This landslide temporarily dammed Arahura River, causing the greatest potential geo-hazard risk of the earthquake event. The results indicate that whilst the sizes of landslides that may initiate in an earthquake generally increase with increasing earthquake magnitude, failure does not require the exceedance of a specific earthquake magnitude threshold. We suggest that landslide initiation is equally dependent on: (1) the susceptibility to failure of the terrain at the time of the earthquake and 2) the specific ground-shaking intensity (MM) experienced. These two factors should be important considerations when planning emergency responses and post-earthquake aerial reconnaissance.

A coupled geomechanics and fluid flow model for induced seismicity prediction in oil and gas operations and geothermal applications

The combined horizontal drilling and hydraulic fracturing has revitalized economically viable production from tight oil and gas shale reservoirs. This joint technology application enabled extensive unconventional resource exploration and development activities first in the United States followed by around the globe for unlocking the vast hydrocarbon resources. While the contributions from these accomplishments also created an enhancement in the local economies and technological advancements, these activities also have raised significant concern on potential surface and groundwater contamination and air pollution issues and more recently induced seismicity for geohazard risk. In this research study, we provide a summary of induced seismic activities related to oil, gas and geothermal operations in the U.S. The role of the stress alteration and behavior of physicochemical interactions taking place between the fracturing fluids used and the shale matrix under stress have been presented using a coupled geomechanics, fluid flow and physicochemical model. Examples of fluid injection in shale reservoir hydraulic fracturing and waste disposal operations have been provided toward better understanding of the predictive methodologies for induced seismicity and preventive effort for sustainable and safe unconventional operations. The impact of the presence of a fault at various distances away from the injection site nearby the disposal and injection operations on occurrence of the induced seismicity was studied. It was shown that microseismic monitoring along with the coupled geomechanics, fluid flow models and statistical analysis of the microseismic data can provide a good lead for prediction of potential fault reactivation and induced seismicity generation in association with oil and gas production, EOR and EGS fluid injection and waste disposal operations.

Stability of Solution Cavities in Urban Developments: A Case Study Towards Enhancing Geohazard Risk Assessment

Karst cavities in fissured soluble rock represent serious geotechnical hazard for civil construction and urban development. The process of cavity formation, expansion, and propagation is difficult to predict because it is driven by a combination of diverse causes, such as the dissolution rate of rock; flow of groundwater; amount of fine material within rock layers; presence of loose, uncontrolled fill over the rock; and the leakage of underground utilities. Several factors can affect cavity stability, including cavity geometry and dimensions, cavity depth, overburden surface-layer lithology, and surface-loading conditions. This paper presents a case study for karst cavities stability in the Abu Dhabi Municipality (ADM) of the United Arab Emirates as part of a comprehensive study initiated by the ADM to address the geotechnical, geologic, and hydrogeological hazards encountered in the municipality. The purpose of this study is to develop a methodology for assessing karst cavities stability in the ADM, and thereby, quantify their potential hazard for civil construction and urban development in the municipality. A numerical study is performed, using a finite difference model that is based on site-specific ground conditions encountered in a localized area. Results from this numerical investigation are presented in the form of stability charts for different lithologic and surface-loading conditions. These charts are used to develop a set of geographic information system cavity-collapse geohazard maps for the study area to factor solution cavity-collapse risk into an integrated geohazard map for the ADM. Based on available information and the case study presented herein, it is concluded that the collapse of solution cavities do not significantly contribute to the geotechnical hazard observed in the ADM.

Application Of Geographic Information Systems (Gis) In Analysis Of Geological Risk Factors And Assessment Of Geohazards In Daugavpils And Ilūkste Districts

This article deals with the main aspects of geological and geomorphological hazards (geohazards) assessment by presenting review of GIS-based methodology for identification and analysis of environmental hazards of such type to which the Daugavpils and Ilūkste districts are exposed. It includes (1) critical review of the availability and state of the art in data sources about geological risk factors, (2) a description of using geomatics methods for obtaining thematic layers of risk factors and techniques of their combining and overlaying, and (3) an analysis and assessment of summary geohazard risk. Such a complex GIS-based studying of geohazards has not been performed before in the territory under study, nor has it been attempted in Latvia. At the same time obtained results allow highlighting areas exposed to geological risk within the Daugavpils and Ilūkste districts, hence providing relevant information for spatial planning of these territories.

Managing Marine Geohazard Risks Throughout the Business Cycle

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173139, “Managing Marine Geohazard Risks Over the Full Business Cycle,” by Andrew W. Hill and Gareth A. Wood, BP America, prepared for the 2015 SPE/IADC Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed. Today, the industry is faced with entry into frontier areas with little prior published understanding and potentially complex slope and deepwater settings. In such settings, early effort in the explorationand- production cycle is required to allow appropriate data to be gathered and assessed. In order to address these issues, BP has adopted a methodology to manage geohazard risks over the life of the license. Introduction In 1964, the rig C.P. Baker was lost in the Gulf of Mexico in a shallow-gas blowout with the loss of 22 lives. That accident, and similar events in the industry around the same time, triggered the development of geophysical site investigation or geohazard methodologies to support safety in tophole drilling and field development through detailed assessment of seabed and near-surface geology. To this end, the Hazards Survey in North America and the Site Survey in Europe became the staple means for evaluating predrill or predevelopment conditions over the following 30 years. The technologies used in these surveys have continued to be developed. These approaches have generally served the industry well for 50 years. However, as the industry has progressed from operations generally on the continental shelf out onto the continental slope and into ultradeep water, the geohazard issues that need to be addressed by the industry have grown in variety and complexity. While the scope of possible sources of geohazards has expanded, so has the potential size of license areas to be studied. If conditions across such blocks on the continental shelf or in ultradeep water were homogeneous, it may be acceptable to continue with the traditional approach of the site survey. However, the conditions in many large blocks are far from homogeneous, and, therefore, a site survey would deliver little understanding of the variability in geohazard conditions and processes that may have implications for the immediate safety of drilling. The longevity of production operations now faced in a license or field has also been gradually extended through the implementation of improvedrecovery techniques. BP’s Magnus field was discovered in the far north of the UK continental shelf in 1974. At the time of first oil in 1983, the projected field life was seen as being out to the mid- 1990s. However, another phase of production drilling will be starting from the platform in 2015, and current projected field life is now seen out to the 2020s. However, the last high-resolution seismic data to have been acquired below the platform were acquired in 1984. Before restarting drilling, a prudent operator would ask the question, “What is the possibility that geohazard conditions may have changed over the last 30 years?” The prudent operator, therefore, needs to revisit geohazard risks and the validity of site-investigation data across the full life of the license, from entry to field abandonment, and to update geohazard understanding consistently across the whole time period. This paper, therefore, sets out an integrated approach to address management of geohazard risks across the life of a license (Fig. 1), an approach that seeks to consistently update understanding of what geohazards might be present, and, thus, where possible, seeks to avoid them directly or mitigate their presence.

Geohazard assessment lifecycle for a natural gas pipeline project

This paper is a walkthrough of the geohazard risk assessment performed for the Front End Engineering Design (FEED) of a planned large-diameter natural gas pipeline, extending from Eastern Europe to Western Asia for a total length of approximately 1,850 km. The geohazards discussed herein include liquefaction-induced pipe buoyancy, cyclic softening, lateral spreading, slope instability, groundwater rise-induced pipe buoyancy, and karst. The geohazard risk assessment lifecycle was comprised of 4 stages: initially a desktop study was carried out to describe the geologic setting along the alignment and to conduct a preliminary assessment of the geohazards. The development of a comprehensive Digital Terrain Model topography and aerial photography data were fundamental in this process. Subsequently, field geohazard mapping was conducted with the deployment of 8 teams of geoprofessionals, to investigate the proposed major reroutes and delve into areas of poor or questionable data. During the third stage, a geotechnical subsurface site investigation was then executed based on the results of the above study and mapping efforts in order to obtain sufficient data tailored for risk quantification. Lastly, all gathered and processed information was overlain into a Geographical Information database towards a final determination of the critical reaches of the pipeline alignment. Input from Subject Matter Experts (SME) in the fields of landslides, karst and fluvial geomorphology was incorporated during the second and fourth stages of the assessment. Their experience in that particular geographical region was key to making appropriate decisions based on engineering judgment. As the design evolved through the above stages, the pipeline corridor was narrowed from a 2-km wide corridor, to a 500-m corridor and finally to a fixed alignment. Where the geohazard risk was high, rerouting of the pipeline was generally selected as a mitigation measure. In some cases of high uncertainty in the assessment, further exploration was proposed. In cases where rerouting was constrained, mitigation via structural measures was proposed. This paper further discusses the cost, schedule and resource challenges of planning and executing such a large-scale geotechnical investigation, the interfaces between the various disciplines involved during the assessment, the innovative tools employed for the field mapping, the classifications developed for mapping landslides, karst geology, and trench excavatability, determining liquefaction stretches and the process for the site localization of the Above Ground Installations (AGI). It finally discusses the objectives of the FEED study in terms of providing a route, a ± 20% project cost estimate and a schedule, and the additional engineering work foreseen to take place in the detailed engineering phase of the project.

Advances in time-lapse geophysics — Introduction

Time-lapse geophysics is becoming an increasingly important and powerful method to measure, monitor, verify, and predict complex time-varying processes in the earth. Applications include resource management (hydrocarbons, groundwater, geothermal…), geohazard risk assessment (natural and induced seismicity, overpressure zones…), environmental issues ( CO 2 sequestration, groundwater contamination and remediation…), geotechnical engineering (dams, roads, bridges…), and fundamental science questions (subsurface flow of fluids, stress and heat, time-variant rock properties, fault dynamics and fracturing, geophysical source mechanisms, near-surface variations in vadose and permafrost zones…). Advances in time-lapse geophysics are being driven by spectacular innovations in theory, data acquisition, and quantitative data analysis. Theoretical innovations include new math and physics developments to properly incorporate 4D space-time variations in modeling, imaging, and inversion methods, and to correctly account for full wavefield or potential field representations of time-lapse geophysical phenomena. Data acquisition innovations include new developments to improve 4D signal/noise levels, and repeat surveys more frequently or continuously, with new source and receiver instrumentation, (semi) permanent arrays, and others. New developments in time-lapse imaging and inversion are allowing us to extract more detailed (and often surprising) information, increasingly in near real-time, to help better understand time-varying processes in the earth’s subsurface. Recent developments in quantitative time-lapse data analysis and interpretation are providing new knowledge to help improve our …

Geohazard Risk Assessment Method Based on Logistic Regression Model

Logistic regression model refers a regress analysis contains two types of variants. In geohazard analysis, each geological factor can be defined as independent variable, whether a geohazard happened or not can be defined as a dependent variable. 1 represents an occurrence of a hazard while 0 represents a hazard doesn’t break out. Because those factors aren’t continual variable, lineal regress is inadequate to deduce the relationship of such kind of independent and dependent variable. Therefore using logistic regress method is a feasible way to solve such technique problem.

A numerical simulation of underwater slope failures generated by salt diapirism combined with active sedimentation

This paper describes advanced finite-element simulations of a geologically active and periodically unstable 700 m high underwater escarpment located in the Gulf of Mexico that has been created by uplifting salt diapirs combined with sediment deposition. The site's geological history, soil permeability and clay shear strength characteristics govern current slope stability, and determine the timing of any future failure. The geological and geotechnical conditions are reported before presenting fully coupled, large-displacement numerical simulations employing critical state formulations of the slope's evolution over the last 600 000 years. The latter form the basis for strain-softening analyses of the pore pressure equalisation and progressive failure processes that control current slope stability. The analyses also address the ground movement patterns that precede instability, giving useful information for geohazard risk assessment and early warning monitoring system design.

Minimize Pipeline Installation Risks in Geohazard Zones

The United States is second only to Japan in economic damages resulting from natural disasters. Proper pipeline installation is critical to mitigate damage in areas prone to natural hazards. This article discusses geohazard risk management (GRM), a proven method for mitigating geohazards (geological or hydrological processes that pose a threat to people and their property) and asset risks.

Long-Term Airborne DInSAR Measurements at X- and P-Bands: A Case Study on the Application of Surveying Geohazard Threats to Pipelines

Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any band and that further time-series analyses can be applied to airborne data. However, most of the airborne DInSAR results, including the time-series, published so far have focused on short-term analyses (baselines within hours or few days). This paper presents the first long-term airborne DInSAR survey at P- and X-band with temporal baselines of 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (PROTRAN), as part of a project to investigate the potential of DInSAR technique to identify, prior to structural damage, geohazards threats to the oil/gas pipelines in Sao Sebastiao-SP, Brazil. After 1 year and 3 months, the P-band data have interferometric coherence equal or greater than 0.3 for approximately 80% of the imaged dense vegetated areas. At X-band, we achieved coherence equal or greater than 0.3 in the urban area. After removing all residual motion errors with proper up-to-date processing, we derived, for the P-band data, land movements with absolute accuracy in the order of centimeters. For X-band we derived land movement measurements with absolute accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these centimeter to millimeter land movements, and how they are related to geodynamic processes and geohazard risks. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for geohazard risk monitoring.

A survey of challenges in reducing the impact of geological hazards associated with earthquakes in Iran

Most of the recent earthquakes in Iran were associated with some types of geological hazards that were the cause of additional damage and casualties in the earthquake-affected areas. In order to reduce the impacts of geo-hazards, several policies and plans were prepared, approved, and implemented by the Iranian government during the last two decades. However, such activities have not yet resulted in risk reduction to an acceptable level; since they are not formulated based on local conditions and are not linked to location-specific comprehensive plans. In this paper, after introducing some of the impacts of geo-hazards associated with recent earthquakes in Iran, the country trends in development of relevant risk reduction plans and policies are introduced, evaluated, and compared with some other countries having similar challenges. Strategies toward risk mitigation in the country are addressed, and a number of indices for the assessment of the geo-hazard risk reduction plans and activities are introduced. Finally, a conceptual model for the evaluation of the preparedness level against geo-hazards is proposed and discussed.

The future of the geosciences

The future of the geosciences and geological research will involve complex scientific challenges, primarily concerning global and regional environmental issues, in the next 20-30 years. It is quite reasonable to suspect, based on current political and socioeconomic events, that young geoscientists will be faced with and involved in helping to resolve some well defined problems: water and energy security, the effects of anthropogenic climate change, coastal sea level rise and development, and the mitigation of geohazards. It is how we choose to approach these challenges that will define our future. Interdisciplinary applied research, improved modeling and prediction augmented with faster and more sophisticated computing, and a greater role in creating and guiding public policy, will help us achieve our goals of a cleaner and safer Earth environment in the next 30 years. In the far future, even grander possibilities for eliminating the risk of certain geohazards and finding sustainable solutions to our energy needs can be envisioned. Looking deeper into the future, the possibilities for geoscience research push the limits of the imagination.

Geohazard identification: the gap between the possible and reality in geophysical surveys for the engineering industry

Offshore Contractors engaged in the business of installing pipelines and subsea structures routinely rely on third party survey data to identify and assess the risk of surface and buried geohazards. In many cases, route or site survey data are supplied to a marine Contractor with the latter having little or no input to the manner in which the geophysical and geotechnical data are acquired, processed and reported. Often, the completed survey reports indicate that neither data acquisition nor the subsequent data processing were carried out with the ultimate goal of the survey or the end user in mind. This lack of focus at the survey stage can contribute to incorrect or over-optimistic assessments of geohazard risk, with serious impact on offshore installation operations as a consequence. Two case studies from the North Sea are discussed where inappropriate data processing and reporting of geophysical data had a negative impact on offshore installation operations; these are used as a basis for a more general discussion of the underlying reasons for the production of engineering survey reports which are “not-fit-for-purpose”.

Treading lightly on shifting ground: The direction and motivation of future geological research

The future of the geosciences and geological research will involve complex scientific challenges, primarily concerning global and regional environmental issues, in the next 20-30 years. It is quite reasonable to suspect, based on current political and socioeconomic events, that young geoscientists will be faced with and involved in helping to resolve some well defined problems: water and energy security, the effects of anthropogenic climate change, coastal sea level rise and development, and the mitigation of geohazards. It is how we choose to approach these challenges that will define our future. Interdisciplinary applied research, improved modeling and prediction augmented with faster and more sophisticated computing, and a greater role in creating and guiding public policy, will help us achieve our goals of a cleaner and safer Earth environment in the next 30 years. In the far future, even grander possibilities for eliminating the risk of certain geohazards and finding sustainable solutions to our energy needs can be envisioned. Looking deeper into the future, the possibilities for geoscience research push the limits of the imagination.

Geo-hazard Risk Evaluation in Huangling County Shaanxi Province

Geo-hazard Risk Evaluation in Huangling County Shaanxi Province

A geomorphological mapping approach for the assessment of seabed geohazards and risk

Exploration and development of offshore hydrocarbon resources has advanced into remote deepwater regions over the last decade and poses significant technical challenges for the design and installation of wells and facilities at extreme water depths. Seafloor and shallow subsurface processes and conditions in these areas are complex and generally poorly understood, and the geohazards to development are larger scale and fundamentally different to those encountered onshore; consequently the geohazard risk to deepwater development projects is potentially significant and requires careful evaluation and mitigation during the front-end planning and engineering design stages of projects. There are no established industry standards or methods for the assessment of geohazards and engineering-quality geophysical data at the scale of development. The paper describes an integrated and systematic map-based approach for the assessment and mitigation of seabed geohazards and risk to proposed deepwater development. The approach employs a multi-disciplinary team working with engineering-quality field calibrated data to accurately map and assess seafloor ground conditions and ensure that development proposals are not exposed to intolerable geohazard risk. The approach taken is very similar to the practice of establishing geological models for land-based engineering projects, in which the complete geological history of the site is used to characterise and predict the performance of the ground. Such an approach is routine for major projects on land but so far does not seem to be common practice in the offshore industry. The paper illustrates the seafloor geomophological mapping approach developed. The products are being used to optimise development layouts to avoid geohazards where possible and to support site-specific engineering design of facilities based on a detailed understanding of the potential geohazard loadings and associated risk.

GIS and remote sensing as tools for conducting geo-hazards risk assessment along Gulf of Aqaba coastal zone, Egypt

Satellite remote sensing data, in addition to Geographic Information Systems (GIS), offers an excellent alternative to conventional mapping techniques in monitoring and mapping of geo-hazards areas. One of the most sustainable development projects in Egypt has been accomplished in Sinai, especially along and around the Gulf of Aqaba and the Gulf of Suez. Variations along the coastal zone of the Gulf of Aqaba have been identified through the analysis of multi-temporal satellite images with the aid of GIS analysis. The study area is subject to rapid and increasing changes in land-use/land-cover that resulting from natural and human activities such as flash flooding, seismic activity, landslides, and tourist and urban activities. This is in addition to the construction projects of roads, ports, PowerStation stations, mineral exploration, beaches, and tourist villages resulting from major environmental impacts. The current study aims to use Remote Sensing and GIS tools to investigate, monitor, and assess geo-hazards through the building of a geographical database. Several techniques have been developed over the last decade mostly to study the geological and geomorphologic characteristics of the terrain; land-use and land-cover changes. These are based on satellite imagery and Digital Elevation Models (DEM) to determine the topographic features, and geo-hazards maps. It is concluded that integrated approaches to monitoring can successfully be used to assess the environmental impacts along the Gulf of Aqaba coastal zone.

Structural architecture of oceanic plateau subduction offshore Eastern Java and the potential implications for geohazards

The region offshore Eastern Java represents one of the few places where the early stage of oceanic plateau subduction is occurring. We study the little investigated Roo Rise oceanic plateau on the Indian plate, subducting beneath Eurasia. The presence of the abnormal bathymetric features entering the trench has a strong effect on the evolution of the subduction system, and causes additional challenges on the assessment of geohazard risks. We present integrated results of a refraction/wide-angle reflection tomography, gravity modelling, and multichannel reflection seismic imaging using data acquired in 2006 south of Java near 113°E. The composite structural model reveals the previously unresolved deep geometry of the oceanic plateau and the subduction zone. The oceanic plateau crust is on average 15 km thick and covers an area of about 100 000 km2. Within our profile the Roo Rise crustal thickness ranges between 18 and 12 km. The upper oceanic crust shows high degree of fracturing, suggesting heavy faulting. The forearc crust has an average thickness of 14 km, with a sharp increase to 33 km towards Java, as revealed by gravity modelling. The complex geometry of the backstop suggests two possible models for the structural formation within this segment of the margin: either accumulation of the Roo Rise crustal fragments above the backstop or alternatively uplift of the backstop caused by basal accumulation of crustal fragments. The subducting plateau is affecting the stress field within the accretionary complex and the backstop edge, which favours the initiation of large, potentially tsunamogenic earthquakes such as the 1994 Mw= 7.8 tsunamogenic event.

Modeling study of growth and potential geohazard for LUSI mud volcano: East Java, Indonesia

The mud volcano known as LUSI first erupted in May 2006 in East Java, Indonesia. The eruption has continued for over two years, and potentially will continue for many years to come, impacting an ever larger area. An obvious and significant question is how extensive the impacted area will become in the coming years. The answer is important for planning scenarios for the relocation of people and infrastructure and for managing the environment and economy. To make such a prediction, an understanding of the geological processes controlling the mud volcanic evolution is needed. A three-dimensional simulation model was built to predict the area affected by the mudflow over a ten-year period, with a special focus on the period from December 2007 until June 2010. The primary model inputs are the mud debit rate, the rate of subsidence and the topography. The model prediction was validated at the December 2007 time step by comparing the results with satellite images from the same period. The simulation was found to provide a good approximation for the mud overflow and growth. The results indicate that the mudflow tends to spread to the west and particularly to the east and north from the currently inundated area. The model predicts that in June 2010 the peak of the mud volcano will have risen 26 m above the original ground level, and the maximum subsidence will have been −63 m below the original ground level. The dynamic subsurface condition in the area creates geohazard risks, and these are also discussed in this paper.