Hazard Assessment Model Research Articles

The SISMA prototype system: integrating Geophysical Modeling and Earth Observation for time-dependent seismic hazard assessment

An innovative approach to seismic hazard assessment is illustrated that, based on the available knowledge of the physical properties of the Earth structure and of seismic sources, on geodetic observations, as well as on the geophysical forward modeling, allows for a time-dependent definition of the seismic input. According to the proposed approach, a fully formalized system integrating Earth Observation data and new advanced methods in seismological and geophysical data analysis is currently under development in the framework of the Pilot Project SISMA, funded by the Italian Space Agency. The synergic use of geodetic Earth Observation data (EO) and Geophysical Forward Modeling deformation maps at the national scale complements the space- and time-dependent information provided by real-time monitoring of seismic flow (performed by means of the earthquake prediction algorithms CN and M8S) and permits the identification and routine updating of alerted areas. At the local spatial scale (tens of km) of the seismogenic nodes identified by pattern-recognition analysis, both GNSS (Global Navigation Satellite System) and SAR (Synthetic Aperture Radar) techniques, coupled with expressly developed models for interseismic phase, allow us to retrieve the deformation style and stress evolution within the seismogenic areas. The displacement fields obtained from EO data provide the input for the geophysical modeling, which eventually permits to indicate whether a specific fault is in a “critical state.” The scenarios of expected ground motion (shakemaps) associated with the alerted areas are then defined by means of full waveforms modeling, based on the possibility to compute synthetic seismograms by the modal summation technique (neo-deterministic hazard assessment). In this way, a set of deterministic scenarios of ground motion, which refer to the time interval when a strong event is likely to occur within the alerted area, can be defined both at national and at local scale. The considered integrated approach opens new routes in understanding the dynamics of fault zones as well as in modeling the expected ground motion. The SISMA system, in fact, provides tools for establishing warning criteria based on deterministic and rigorous forward geophysical models and hence allows for a well-controlled real-time prospective testing and validation of the proposed methodology over the Italian territory. The proposed approach complements the traditional probabilistic approach for seismic hazard estimates, since it supplies routinely updated information useful in assigning priorities for timely mitigation actions and hence it is particularly relevant to Civil Defense purposes.

Human Embryonic Stem Cell Derived Hepatocyte-Like Cells as a Tool for In Vitro Hazard Assessment of Chemical Carcinogenicity

Hepatocyte-like cells derived from the differentiation of human embryonic stem cells (hES-Hep) have potential to provide a human relevant in vitro test system in which to evaluate the carcinogenic hazard of chemicals. In this study, we have investigated this potential using a panel of 15 chemicals classified as noncarcinogens, genotoxic carcinogens, and nongenotoxic carcinogens and measured whole-genome transcriptome responses with gene expression microarrays. We applied an ANOVA model that identified 592 genes highly discriminative for the panel of chemicals. Supervised classification with these genes achieved a cross-validation accuracy of > 95%. Moreover, the expression of the response genes in hES-Hep was strongly correlated with that in human primary hepatocytes cultured in vitro. In order to infer mechanistic information on the consequences of chemical exposure in hES-Hep, we developed a computational method that measures the responses of biochemical pathways to the panel of treatments and showed that these responses were discriminative for the three toxicity classes and linked to carcinogenesis through p53, mitogen-activated protein kinases, and apoptosis pathway modules. It could further be shown that the discrimination of toxicity classes was improved when analyzing the microarray data at the pathway level. In summary, our results demonstrate, for the first time, the potential of human embryonic stem cell--derived hepatic cells as an in vitro model for hazard assessment of chemical carcinogenesis, although it should be noted that more compounds are needed to test the robustness of the assay.

Kalman filter decision systems for debris flow hazard assessment

This paper aims to develop a model for debris flow hazard assessment, since Taiwan is a mountainous country subject to bouts of heavy rainfall during the rainy and typhoon seasons and is thus frequently subject to landslide disasters. The database used is comprised of information from actual cases that occurred in areas of Hualien in eastern Taiwan during 2007 and 2008. The Kalman filter model is utilized to assess the occurrence of debris flows from computed indexes, to verify modeling errors. Comparisons are made between two models to determine which one is better in practical applications. The efficiency of the Kalman filter decision system has been proved, showing smaller average relative error and correspondingly larger ratio of success on debris flow assessment when compared to the neural network model. The relative error is calculated between the differences in the ratio of model outputs and that of actual occurrences. Such an error index can be decreased from 4.65 to 3.39% by introducing the concept of geographic divisions to the Kalman filter model, which demonstrates its ability to forecast the occurrence of debris flows for the coming year.

Evaluating quantitative and qualitative models: An application for nationwide water erosion assessment in Ethiopia

This paper tests the candidacy of one qualitative response model and two quantitative models for a nationwide water erosion hazard assessment in Ethiopia. After a descriptive comparison of model characteristics the study conducts a statistical comparison to evaluate the explanatory power of the models, using an Ethiopian soil erosion data set as reference. The study, therefore, introduces a generic transformation procedure, whereby qualitative models reproduce quantitative results, while the outcomes of quantitative models are mapped on an ordered (qualitative) classification. The evaluation yields the following results. Application of the USLE model in Ethiopia is restricted by data paucity, while it ranks lowest in the statistical evaluation. However, it provides reliable results in areas where water erosion incidence is low. The Expert model, based on easily available data and expert judgements, covers a wide variability of the explanatory variables, which makes it suitable for a nationwide assessment. It is the second-best model in the statistical evaluation. Yet, its qualitative output complicates the assessment of the dynamic changes in soil productivity characteristics, while the postulated additive form of the logit model is not appropriate to assess erosion hazard. The quantitative AccDat model has the highest predictive power and is based on easily available data, but has a frail empirical basis and its application at a nationwide scale requires a careful interpretation. The varying performances in the different areas of the data domain justify the selection of a combination of models for a nationwide erosion assessment, rather than a single ‘best’ model.

Drought hazard assessment and spatial characteristics analysis in China

Based on the monthly precipitation data for the period 1960–2008 from 616 rainfall stations and the phenology data of main grain crops, the spatial characteristics of drought hazard in China were investigated at a 10 km×10 km grid-cell scale using a GIS-based drought hazard assessment model, which was constructed by using 3-month Standard Precipitation Index (SPI). Drought-prone areas and heavy drought centers were also identified in this study. The spatial distribution of drought hazard in China shows apparent east-west difference, with the eastern part of China being far more hazardous than the western part. High hazard areas are common in the eastern and central parts of Inner Mongolian Plateau, the central part of Northeast China Plain, the northern part of Heilongjiang, the southeastern part of Qinghai-Tibet Plateau, the central and southern parts of Loess Plateau, the southern part of North China Plain, the northern and southern parts of Yangtze River Plain, and Yunnan-Guizhou Plateau. Furthermore, obvious differences in drought hazard were found both within and between different agricultural zonings.

A fuzzy clustering iterative model using chaotic differential evolution algorithm for evaluating flood disaster

Flood disaster is a kind of frequent natural hazards. The objective of flood disaster evaluation is to establish hazard assessment model for managing flood and preventing disaster. Base on the chaotic optimization theory, this paper proposes a chaotic differential evolution algorithm to solve a fuzzy clustering iterative model for evaluating flood disaster. By using improved logistic chaotic map and penalty function, the objective function can be solved more perfectly. Two practical flood disaster cases have been taken into account so as to test the effect of novel hybrid method. Simulation results and comparisons show that the chaotic differential evolution algorithm is competitive and stable in performance with simple differential evolution and other optimization approaches presented in literatures.

Intraevent Spatial Correlation of Ground-Motion Parameters Using SK-net Data

Abstract Spatial correlation of intraevent peak ground-motion amplitudes at different sites is an important issue for seismic hazard and risk assessment of spatially distributed buildings and infrastructure. Correlated seismic effects cause acute concentration and accumulation of seismic losses, potentially resulting in a catastrophic event. We investigate the adequacy of the existing spatial correlation model of Goda and Atkinson (2009b) for Japanese earthquakes in light of strong ground motion data obtained from the SK-net database, which achieves greater spatial density of recording stations in the Kanto region. The SK-net dataset is suitable for filling in gaps in the Goda–Atkinson dataset at short separation distances where data coverage is sparse. Spatial correlations based on the SK-net data decrease gradually with increasing interstation separation distance. At short separation distances, the estimated spatial correlation data points show large variability around the average trend. Sensitivity to the manner of estimating intraevent standard deviation is significant, as positive correlations among residuals occur due to the dense spatial coverage of recording stations. The developed spatial correlation model fits the observed data reasonably well and is consistent with the Goda–Atkinson model. At short separation distances (less than 1 km), wherein empirical data are limited and estimates are uncertain, discretion is required in adopting such models for seismic hazard and risk assessment of spatially distributed structures.

A GIS model for preliminary hazard assessment of swelling clays, a case study in Harran plain (SE Turkey)

Swelling behavior of clayey soils regarded as a hidden disaster, causes a great deal of damage in light hydraulic structures such as drinking water network, irrigation pipes or open canal linings through which water can easily leak and penetrate into soil during loading and unloading stages. Early identification during site investigation and laboratory testing is extremely important to ensure that the appropriate design strategy is adopted. The clay soils having swelling potential are generally found in arid and semi-arid regions, such as in the Şanliurfa-Harran plain located in the southeast of Turkey. The problems associated with swelling clays occurred for the lightweight hydraulic structures constructed in Turkey have been met during the construction of irrigation structures in the scope of Southeast Anatolian Project as the Turkey’s greatest water resources project. Therefore, the identification of such soils and the assessment of their swelling potential parameters are necessary for hazard mitigation planning and land-use management. In this scope, extensive geotechnical study is executed for an investigation area. The samples were obtained from the Harran plain where many irrigation canal structures are constructed, and geotechnical study was performed on these samples. Atterberg limit tests often provide the basic field information to substantiate the soil’s swelling nature. The plasticity index (PI) and liquid limit (LL) values are also used extensively for classifying swelling soil and should always be determined during preliminary investigations. Because of this, LL and PI are assessed by using geographical information system (GIS)-based computer software, and LL and PI contour maps are created. Swelling percentages of the soil samples were carried out on both undisturbed and compacted soil samples by using direct methods. As a result of this extensive study, the values of swelling percentages determined for each location are used to obtain the swelling potential hazard map of the area by means of a GIS program. The results of GIS analyses for this area indicate that the analyses based on a lot of data introduce meaningful results for this study. It is expected that these maps will be a useful tool for planners and engineers in their efforts to achieve better land-use planning and to decide necessary remedial measures.

Long‐term slip history discriminates among occurrence models for seismic hazard assessment

Today, the probabilistic seismic hazard assessment (PSHA) community relies on stochastic models to compute occurrence probabilities for large earthquakes. Considerable efforts have been devoted to extracting information from long catalogs of large earthquakes based on instrumental, historical, archeological and paleoseismological data. However, the models remain only and insufficiently constrained by these rare single‐slip event data. Therefore, the selection of the models and their respective weights necessarily involves ruling by a panel of experts. Since cumulative slip data with high temporal and spatial resolution are now available, we propose a new approach to incorporate these pieces of evidence of mid‐ to long‐term fault behavior into PSHA: the Cumulative Offset‐Based Bayesian Recurrence Analysis (COBBRA). For the Dead Sea Fault, our method provides weights to the competing recurrence and rupture models, allows time‐independent models to be ruled out, and provides a means to compute the cumulative probability of occurrence for the next full‐segment event reflecting all available data.

Quantitative landslide hazard assessment along a transportation corridor in southern India

A quantitative model for landslide hazard assessment on natural slopes is presented for a transportation corridor of the Nilgiri Hills in southern India. The data required for the hazard assessment were mostly obtained from historical records. For the hazard modeling, a landslide inventory map was prepared from technical reports and maintenance records for a road and a railroad, available for a 21 year period from 1987 to 2007. Most landslides are shallow translational debris slides and debris flow slides triggered by rainfall. On natural slopes landslides occurred as first-time failures. A logistic regression model was used to determine the spatial probability of landslides for each pixel by taking the source area of the existing landslides as dependent, and slope angle, aspect, regolith thickness and land use as independent variables. The temporal probability of landslides was estimated indirectly using the exceedance probability of the rainfall threshold required to trigger landslides for the first time on natural slopes. The probability of landslide size was estimated as frequency percentage of landslide volume, a proxy for landslide magnitude, and the percentage values were then expressed as probability. By assuming independence among the three probabilities, a quantitative estimate of a landslide hazard was obtained as the joint probability of landslide volume, of landslide occurrence in an established time period and of spatial probability of a landslide initiation. The models were validated using the rainfall and landslide events that occurred during 2008 and 2009. Total 12 specific landslide hazard maps were generated considering six time periods (1, 3, 5, 15, 25 and 50 years), and two landslide volumes (volume exceeding 1000 m 3 and 10,000 m 3).

A new methodology for flood hazard assessment considering dike breaches

This study focuses on development and application of a new modeling approach for a comprehensive flood hazard assessment along protected river reaches considering dike failures. The proposed Inundation Hazard Assessment Model (IHAM) represents a hybrid probabilistic‐deterministic model. It comprises three models that are coupled in a dynamic way: (1) 1D unsteady hydrodynamic model for river channel and floodplain between dikes; (2) probabilistic dike breach model which determines possible dike breach locations, breach widths and breach outflow discharges; and (3) 2D raster‐based inundation model for the dike‐protected floodplain areas. Due to the unsteady nature of the 1D and 2D models and runtime coupling, the interdependence between the hydraulic loads on dikes at various locations along the reach is explicitly considered. This ensures a more realistic representation of the fluvial system dynamics under extreme conditions compared to the steady approaches. The probabilistic dike breach model describes dike failures due to three failure mechanisms: overtopping, piping and slope instability caused by seepage flow through the dike core (micro‐instability). The 2D storage cell model computes various flood intensity indicators such as water depth, flow velocity, and inundation duration. IHAM is embedded in a Monte Carlo simulation in order to account for the natural variability of the input hydrograph form and the randomness of dike failures. Besides binary (wet/dry) inundation patterns, IHAM generates new probabilistic flood hazard maps for each intensity indicator and the associated uncertainty bounds. Furthermore, the novel probabilistic dike hazard maps indicate the failure probability of dikes for each considered breach mechanism.

A unique 4000 year long geological record of multiple tsunami inundations in the Augusta Bay (eastern Sicily, Italy)

We present the geological evidence for a 4000 year long record of multiple tsunami inundations along the coast of the Augusta Bay (eastern Sicily) and discuss its implications. The research was carried out through a multi-theme approach which benefited from an extraordinarily long historical record that we used to guide detailed geomorphologic and geologic surveys, coring campaigns and laboratory analyses. Two sites, named the Augusta Hospital and Priolo Reserve, were selected and investigated in detail along the 25 km-long coastline of Augusta Bay. We found evidence for six (possibly seven) tsunami deposits; three of them may be tentatively associated with the 1693 and 365 AD Ionian Sea historical tsunamis and the ~ 3600 BP Santorini event. The other three (possibly four) deposits are evidence for unknown paleo-inundations dated at about 650–770 AD, 600–400 BC and 975–800 BC (at Augusta Hospital site), and 800–600 BC (at Priolo Reserve site). We use these ages to extend further back the historical record of tsunamis available for this coastal area. The exceptional number of tsunami deposits found with this study allowed us to derive an average geologic tsunami recurrence interval in the Augusta Bay of about 600 years for the past 4 ka. Conversely, the historical tsunami data for the past millennium suggest an average tsunami recurrence interval of about 250 years. This difference in the average recurrence intervals suggests that only the strongest inundations may leave recognizable geological signatures at the investigated sites (i.e. the evidence for the 1908 and 1169 tsunamis is missing) but also that the geomorphological setting of the site and its erosional/depositional history are critical aspects for the data recording. Thus, an average recurrence interval derived from the geological record should be considered as a minimum figure. The identification and age estimation of tsunami deposits represent a new and independent contribution to tsunami scenarios and modeling for coastal hazard assessment in Civil Protection applications. Furthermore, our study cases provide new elements on tsunami deposit recognition related to exceptionally large events that occurred in the Aegean Sea.

A GIS Based Cost Distance Modeling for Oil Spill Hazard Assessment in the Coastal Areas of South Eastern Nigeria

A GIS Based Cost Distance Modeling for Oil Spill Hazard Assessment in the Coastal Areas of South Eastern Nigeria

Hybrid slip model for near-field ground motion estimation based on uncertainty of source parameters

The hybrid slip model used to generate a finite fault model for near-field ground motion estimation and seismic hazard assessment was improved to express the uncertainty of the source form of a future earthquake. In this process, source parameters were treated as normal random variables, and the Fortran code of hybrid slip model was modified by adding a random number generator so that the code could generate many finite fault models with different dimensions and slip distributions for a given magnitude. Furthermore, a simple method to choose an optimal one from these generated models was proposed. The 1994 Northridge earthquake was taken as an example to demonstrate the procedure of the application of the improved model. Three rock stations, LV3, MCN and PCD, in near-field were used to compare the simulated ground motion from the improved model and optimal model with the observed one. The agreement between them in the periods of interest indicates that the improved model and the method to choose the optimal model are available for the engineering practice of ground motion estimation.

Simulation of Strong Wind Field by Non-hydrostatic Mesoscale Model and Its Applicability for Wind Hazard Assessment of Buildings and Houses

The strong wind field caused by Typhoon Songda, which passed through Kyushu in Japan in 2004, was simulated numerically. A non-hydrostatic mesoscale model was used for the numerical simulation. The simulated wind field was compared with the observed wind field in terms of wind speeds and directions, which were measured by the wind observation network, NeWMeK. It was found that the temporal variation of the calculated wind speeds at 1 km hori-zontal mesh grids correspond to the average of the observed wind speeds over a ten to fifteen minute time period. The temporal variation of the calculated wind directions showed good agreement with the observations. The maximum values of the calculated wind speeds were highly correlated to the maximum values of the observed wind speeds. The applicability of the mesoscale model for the wind hazard assessment of buildings was examined, and it was found that the maximum values of the calculated wind speeds at higher altitudes showed higher correlations with the rates of damaged houses caused by Typhoon Songda.

Geomorphological landslide models for hazard assessment: a case study at Cloudy Hill, Hong Kong

Abstract Geomorphological landslide models developed to characterize natural hill slope landslides can assist significantly in the evaluation of natural hill slopes for hazard and risk assessment and for the selection of appropriate mitigation measures. Intense rainstorms in 2000 and 2001 resulted in about 45 natural hill slope landslides on a small area in the vicinity of Cloudy Hill, Tai Po, Hong Kong. A detailed study was carried out to examine systematically the characteristics and mechanisms of the landslides for the purposes of identifying the geomorphological and geological factors influencing susceptibility to landslide occurrence and with the aim of improved hazard assessment for similar hill slopes elsewhere in Hong Kong. Site-specific landslide models were developed from an assessment of the geomorphological setting and landslide characteristics, using a combination of morphological and morpho-chronological mapping based on aerial photograph interpretation together with field reconnaissance and inspection. Detailed field mapping was carried out for selected landslides following initial review, to confirm the relevant geomorphological factors and document relevant landslide characteristics. An outline of the study at Cloudy Hill is given and the development of the landslide models is presented, together with an overview of how the models were used to assist in the evaluation of natural terrain landslide hazards.

Hazard assessment model for debris flow prediction

Debris flow disasters have plagued Taiwan in recent decades, and caused casualties and destruction of property. Several methods, including the numerical method, statistical method, and experimental method, have been adopted in recent years to predict debris flow, and more recently, the neural network (NN) and the genetic algorithm (GA) methods have been introduced to simulate the occurrence of debris flows. This study proposes using the GA to weigh seven important variables according to principles similar to natural selection. The study then simultaneously inputs these variables into a NN model to predict debris flow occurrences based on relevant factors. There were 154 potential cases of debris flow collected from eastern Taiwan and fed into the model for testing. The average ratio of successful prediction reached 94.94%, which demonstrates that the proposed model can provide stable and reliable results for predicting debris flow in hazard mitigation and guard systems.

Development of a seismic source model for probabilistic seismic hazard assessment of nuclear power plant sites in Switzerland: the view from PEGASOS Expert Group 4 (EG1d)

We present a seismogenic source model for site-specific probabilistic seismic hazard assessment at the sites of Swiss nuclear power plants. Our model is one of four developed in the framework of the PEGASOS project; it contains a logic tree with nine levels of decision-making. The two primary sources of input used in the areal zonation developed by us are the historical and instrumental seismicity record and large-scale geological/rheological units. From this, we develop a zonation of six macrozones, refined in a series of seven decision steps up to a maximum of 13 zones. Within zones, activity rates are either assumed homogeneous or smoothed using a Gaussian kernel with width of 5 or 15 km. To estimate recurrence rate, we assume a double truncated Gutenberg-Richter law, and consider five models of recurrence parameters with different degrees of freedom. Models are weighted in the logic tree using a weighted Akaike score. The maximum magnitude is estimated following the EPRI apporach. We perform extensive sensitivity analyses in rate and hazard space in order to assess the role of declustering, the completeness model, quarry contamination, border properties, stationarity, regional b-value and magnitude-dependent hypocentral depth.

Development of a hazard assessment model for near surface caves in limestone

Gaziantep is the sixth crowded city of Turkey with a population of about one million. The city contains several near surface man made caves excavated into Oligocone and Miocone age limestone. During the development of the city, many structures were constructed over these caves. Some of them collapsed and caused injuries, lost of life, and properties. The city is still under threat of new collapse of caves and tragedies. This paper describes the methodology developed to prepare geohazard map of potential cave collapse. Developed methodology was based on the determination of global factor of safety (FS) of the cave roofs against failure. Numerical analysis was carried out using 3D finite element method. Three hazard levels were proposed depending on the range of calculated FS namely low, moderate and, high. Geographical Information System (GIS) was used to produce hazard map of caves. The validation of the proposed hazard levels was tested with previously collapsed cave and reasonably good agreement was found. This study is believed to make a great contribution to local municipalities for future development planning of the city.

A Method for Developing Regional Road-Fill Failure Hazard Assessments Using GIS and Virtual Fieldwork

Road-fill failure is a common and potentially catastrophic hazard on mountainous roads. Land managers need methods for assessing road-fill failure hazards that minimize time in the field and that use readily available data. We developed a probabilistic hazard assessment method using virtual fieldwork and LiDAR-derived slope distributions over a 97-km length of the Blue Ridge Parkway in North Carolina. The locations of arc-shaped pavement cracks and previous road-fill failures were mapped using field-verified VisiData video reconnaissance, and the slopes surrounding failed-or-cracked sites were extracted from a digital elevation model and compared to uncracked portions of road. The site-median slopes of the failed-or-cracked sites and uncracked sites are normally distributed and significantly different (P < 0.01) from one another. This observation provides the basis for a probabilistic, hazard assessment model that uses the site-median slope of a 30-m–diameter buffer to categorize currently uncracked sites as either stable or at risk of road-fill failure during future high-intensity rainfall events.