Evaluation Of Natural Hazards Research Articles

Evaluating the contribution of geophysics to the assessment of natural hazards

This paper discussed the role of geophysics in the evaluation of natural hazards with the view to enhancing familiarity with earth shakes, ground characteristics, landslide likelihood, and volcanic deliveries. Semantic and geophysical data were collected from seismic surveys, measurement of groundwater, electrical resistivity of the subsoil and gas emission. Seismic data analysis revealed diverse activity across sites, with magnitudes ranging from 3.234 to 6.456 Mw, emphasizing the importance of geophysical monitoring in identifying high-risk areas. Groundwater measurements indicated spatial variations in water table depth from 1.234 to 6.789 m, essential for effective resource management. Soil resistivity values ranged from 75.123 to 145.901 Ohm-m, providing insights into soil properties relevant for geotechnical and environmental studies. Landslide susceptibility assessment used the factor of slope angle, vegetation cover, and rainfall intensity; these were 10. 901° to 28. 345°, 55. 234% to 88. 456%, and 6. 789 to 20. 901 mm/hr respectively. The gas emission of SO2 ranged between 0. 123–0. 901 kg/s, that of CO2, 0. 456–1. 234 kg/s, while H2S ranged between 0. 789–1. 567 kg/s based on the emission of the several sites suitable for eruption prediction models. A statistical approach was used in which Histogram, scatter plot and radar chart were used to explain the data collected. The study conclude that the application of various geophysical methods is strikingly useful in natural hazard and risk assessment and planning and therefore beneficial in reducing disaster risks. These results provide compelling evidence about the importance of geophysics in propagating awareness in the Earth processes and improvement of hazards.

Kvartérní sedimenty a nálezy rostlinných fosilií v Salvadoru, Střední Amerika

Development cooperation projects implemented by the Czech Geological Survey in the area of Central America, focused on the evaluation of natural hazards, took place in the years 1997–2009. They started in Nicaragua (since 1997), continued in El Salvador (since 2003) and then also in Costa Rica (since 2006). The results of these projects were always handed over to local organizations (INETER, SNET and MINAE) in the form of final reports, and summarized last year in the book by Hradecký et al. 2021. As a supplement to this book, we present here some other findings of projects in El Salvador (from the years 2003–2005) that did not fit into its scope. They relate to the geology of Quaternary sediments and interesting findings of plant fossils preserved in the Neogene volcanosedimentary complexes. In the 2003 stage, work took place in the Gulf of Fonseca in south- -eastern part of El Salvador, with the dominant volcano Conchagua and the important port of La Unión. In addition to classic Quaternary sediments, the following phenomena were described: oyster hems (rims) around the islands of Periquito and Perico, volcaniclastic rocks (“tobas”) fallen into the lake environment near the Los Chorros lagoon (Břízová et al. 2004), and polygenetic sediments on the slopes of the formerly active volcano Conchagua, showing the existence of debris flows and lahars. Plant fossils have been found at one locality only, in fine-grained ash deposits of the maar sequence near El Naranjo (Figs 1 to 3). In the 2004 stage, work took place inland, in an area north of the capital city San Salvador, with the dominant volcano Guazapa. In addition to the classical Quaternary sediments, the following phenomena were described: polygenetic sediments of the depressions north of the town of Aguilares (Figs 4 to 9) and outcrops of lake sediments, exposed in the north of the studied territory on steep slopes near the Río Lempa dam (Fig. 10), south-east of the city of Colima (Havlíček – Vorel 2005). In the same area, on the bank of the dam near the town of San Cristobal, interesting consolidated (cemented) mudflows with the occurrence of fossil wood were also documented (Figs 11 and 12). In the year 2004, a paleontological expedition to the Río Sisimico canyon, about 40 km to the SE from the primarily studied area (Figs 13 to 16), was also carried out. The findings of plant remains from this locality are shown in Figs 17 to 22. Plant remains were further found at two localities in the primarily studied area: Suchitoto (Figs 23 to 29) and in the area south of El Molino (only indeterminable remains). Charred (and buried) tree trunks were also found in the white pumice tuffs called “Tierra Blanca” in several places of the studied area (Fig. 30). In the 2005 stage, the work took place in the north-western part of El Salvador, near the borders with Guatemala and Honduras, in the vicinity of the Metapán city. In addition to classic Quaternary sediments (Figs 31 and 32), the following phenomena were described: three generations of alluvial fans (alluvial gravels and sands) near the Metapán city, “kettle holes” created by water erosion in the river bottom (Fig. 33) and aeolian (wind-deposited) sediments from the Matalapa desert. The most interesting, however, were the secondarily tilted (and not yet fully consolidated) gravels and sands of the oldest generation of alluvial fans in the south-western surroundings of the city of Metapán (Figs 34 to 39). In the open cut along the CA12 road to Metapán (La Pedrera area, Fig. 40), small, although indeterminable remains of flora and possibly also fauna (fish scales?) in diatomite-like rocks were found. However, the locality is promising for future research. All the findings published in this paper were also mentioned in the final reports which were handed over in Spanish translation to the Salvadoran SNET institution (Hradecký et al. 2003, 2004 and 2005).

Unified hazard models for risk assessment of transportation networks in a multi-hazard environment

Transportation networks play a vital role in the economic prosperity of modern societies. Recent hazardous events in Greece, for instance, the 2021 Crete earthquake, the 2021 Thessaly earthquakes and floods, and the heavy 2019 rainfall in Crete, have revealed the vulnerability of roadway networks to natural hazards, resulting in severe physical damage and important economic and societal losses. Severe damage on bridges and tunnels of roadway networks is commonly related to the effects of multiple hazards that may act independently during their life span. However, the literature on risk assessment of the above elements commonly focuses on the effects of a single hazard, disregarding the effects of various hazards in a multi-hazard environment. In this context, there is an increasing need for a reasonable and practical evaluation of the multi-hazard risk of transportation infrastructure. Research project INFRARES (https://www.infrares.gr/) aspires to gain further insight into the risk and resilience assessment of bridges and tunnels subjected to independent and/or multiple subsequent natural hazards, proposing a comprehensive framework toward a more efficient risk assessment of the above critical transportation infrastructure components. This paper presents the first part of the framework. More specifically, a unified methodology for the development and graphic presentation of single seismic- and flood-hazard scenarios, as well as of novel multi-seismic-flood hazard scenarios, are presented, providing a valuable tool for risk assessment of roadway networks for separate, combined (triggered), or subsequent hazards. The unified approach followed to develop single seismic and flood hazard scenarios is initially presented. The data required to develop such scenarios are derived from recently published and freely available data accessible via European databases; hence, allowing for a straightforward application of the proposed methodology throughout Europe. The unified approach in developing single hazard scenarios is further exploited to develop integrated seismic-flood hazard scenarios. Single and multi-hazard scenarios are graphically displayed in the form of GIS format maps, with the methodology being applied to the Greek terrain for various hazard scenarios. Recent hazard events that caused significant damage to the Greek road network are also presented to emphasize the importance of proper evaluation of natural hazards and their effects on roadway networks in multi-hazard environments. The methodology developed within this study contributes toward the generation of uniform multi-hazard scenarios for the risk assessment of various structures and networks in a multi-hazard environment.

Seismic record approach for the evaluation of natural hazards: a key study from SW Anatolia/ Turkey

Seismic record approach for the evaluation of natural hazards: a key study from SW Anatolia/ Turkey

Remote assessment of natural hazards on the base of the mathematical morphology of landscape

The aim of this paper is to show approaches for the quantitative evaluation of natural hazards using the remote sensing data and basing on the results of the mathematical morphology of landscape. The mathematical model of the morphological pattern for lacustrine thermokarst plains with fluvial erosion was taken for the decision of the problem in case of an asynchronous start of the thermokarst process with the continuous generation of new thermokarst depressions.
 The mathematical analysis of assumptions taken in the model gives us the regularities of the morphological pattern for the thermokarst plains with fluvial erosion including exponential distribution for khasyrei areas, integral-exponential distribution for lake areas, and the Poisson distribution for a quantity of either khasyreis or lakes within the key sites. Besides, analyzing the development of the territory in question by the approaches used in mathematical morphology of landscape we found out that in case of asynchronous start under very general conditions a dynamic equilibrium is established in generating thermokarst lakes and turning them into khasyreis after a long time. At the same time, the distribution density of thermokarst foci and their sizes, as well as process damage and the dimensions of khasyreis tend to some final levels specified by the expressions described above.
 The results obtained were empirically tested at 17 key sites. Generally, the empirical testing shows that the asynchronous start takes place within thermokarst plains with fluvial erosion at a sufficient number of sites, and the theoretically obtained regulations are valid.
 The regulations obtained were used for the mathematical solution of the probabilistic task for damage of a linear structure crossing the thermokarst plain with fluvial erosion.

Interseismic Ground Deformation and Fault Slip Rates in the Greater San Francisco Bay Area From Two Decades of Space Geodetic Data

AbstractThe detailed spatial variations of strain accumulation and creep on major faults in the northern San Francisco Bay Area (North Bay), which are important for seismic potential and evaluation of natural hazards, remain poorly understood. Here we combine interferometric synthetic aperture radar data from the ERS‐1/2 and Envisat satellites between 1992 and 2010 with continuous and campaign GPS data to obtain a high spatial and temporal coverage of ground deformation of the North Bay. The SAR data from both ascending and descending orbits are combined to separate horizontal and vertical components of the deformation. We jointly invert the horizontal component of the mean velocities derived from these data to infer the deep strike‐slip rates on major locked faults. We use the estimated deep rates to simulate the long‐wavelength deformation due to interseismic elastic strain accumulation along these locked faults. After removing the long‐wavelength signal from the InSAR horizontal mean velocity field, we estimate fault‐parallel surface creep rates of up to 2 mm/year along the central section of the Rodgers Creek fault and surface creep rates ranging between 2 and 4 mm/year along the Concord fault. No surface creep is geodetically resolved along the West Napa and Green Valley fault zones. We identified characteristically repeating earthquakes on the Rodgers Creek fault, the West Napa fault, the Green Valley fault, and the Concord fault. Nontectonic deformation in the Geysers geothermal field and in Late Cenozoic basins (Rohnert Park and Sonoma basins) are also observed, likely due to hydrological and sediment‐compaction processes, respectively.

Application of geographical information system for mapping/monitoring seismological hazards in Pakistan

This study attempts to use the geographic information system (GIS) technique to map and understand the tectonics and crustal structures of Pakistan. Maps of surficial tectonic features and seismological parameters including Moho depth, Pn velocity and Pg velocity are complied. Based on the seismological data-set of the country the earthquake hazard map of Pakistan is also presented by applying regression technique on seismological, geological and topographical parameters. A case study of 8 October 2005 earthquake is used to validate the hazard map. It is envisaged that the developed GIS database would help policy-makers and scientists in natural hazard evaluation, seismic risk assessment and understanding of earthquake occurrences in Pakistan.

Assessment of Seismic Damage of Buildings and Related Environmental Impacts

AbstractSustainable development studies have recently begun to consider damage loss attributable to natural hazards. A sustainable perspective on building design entails an understanding of a structure’s life-cycle environmental costs and consideration of the associated environmental impacts induced by natural hazards. Damage repair costs lead to additional material and energy consumption, creating harmful environmental impacts. Merging the results obtained from a natural hazard evaluation and related environmental impacts for buildings in seismically prone areas provides a novel outlook for sustainable design decisions. To evaluate the environmental impacts caused by buildings, the long-term effects accrued throughout a building’s lifetime and the effects associated with damage repair need to be quantified. A literature review and a proposed method for this type of analysis have been developed and are discussed. Using Athena and HAZUS-MH software, this study evaluated the performance of steel and concret...

Lithological mapping and fuzzy set theory: Automated extraction of lithological boundary from ASTER imagery by template matching and spatial accuracy assessment

Lithological boundaries provide information useful for activities such as mineral and hydrocarbon exploration, water resource surveys, and natural hazard evaluation. Automated detection of lithological boundaries reduces bias inherent in expert interpretation of boundaries and thus improves the reliability of lithological mapping. The Rotation Variant Template Matching (RTM) algorithm was applied to ASTER imagery to detect pre-defined lithological boundaries. Templates incorporating the mineral combinations gypsum–calcite and calcite–illite were designed to detect boundaries between evaporites, marly limestone, and sandstone. The RTM algorithm successfully detected lithological boundaries by rotating the templates over the ASTER imagery. The accuracy of the detected boundaries was spatially assessed using fuzzy set theory. Boundaries from a published geological map and boundaries interpreted from a stereo pair of aerial photos by five experts were used as references for assessing the accuracy. A confidence region unifying spatial errors was defined for the geological map and stereo-pair interpretation to provide boundary zones from these references. The correspondence between detected boundaries and the boundary zones of the aerial photo was better than between detected boundaries and boundary zones of the geological map.

Sampling Bias and Class Imbalance in Maximum-likelihood Logistic Regression

Logistic regression is a widely used statistical method to relate a binary response variable to a set of explanatory variables and maximum likelihood is the most commonly used method for parameter estimation. A maximum-likelihood logistic regression (MLLR) model predicts the probability of the event from binary data defining the event. Currently, MLLR models are used in a myriad of fields including geosciences, natural hazard evaluation, medical diagnosis, homeland security, finance, and many others. In such applications, the empirical sample data often exhibit class imbalance, where one class is represented by a large number of events while the other is represented by only a few. In addition, the data also exhibit sampling bias, which occurs when there is a difference between the class distribution in the sample compared to the actual class distribution in the population. Previous studies have evaluated how class imbalance and sampling bias affect the predictive capability of asymptotic classification algorithms such as MLLR, yet no definitive conclusions have been reached.

Effects of the 6th September 2002 earthquake: damage amplification in the south-eastern sector of Palermo explained by GIS technology

During the 6th September 2002 earthquake the highest damage level in Palermo was observed in the SE sector. This is a recent urbanization area where reinforced concrete structures predominate. A detailed analysis of soil properties in Palermo was carried out by City-GIS to investigate a possible role of nearsurface geology on earthquake effects. City-GIS is a tool dedicated to natural hazard evaluation in urban areas. The availability of high density of well log data (stratigraphic and geotechnical) allowed a realistic modeling of surface geology and physical-mechanical properties that control the seismic response. In wide zones of the above mentioned sector of Palermo, outcropping terrains are composed of thin calcarenite layers, lying above remarkably thick siltyclayey sands that overlay the Numidian Flysch, commonly considered the bedrock of Quaternary sediments. Since silty-clayey sands feature greater deformability properties (Young's modulus) and smaller resistance properties (undrained cohesion and shear resistance angle) than Numidian Flysch, these zones of the SE sector exhibit high values of the acoustic impedance contrast. Moreover, a quite wide portion of the study area, crossed by the Oreto River, is characterized by very thick alluvial deposits. Here, the significant lateral variations of the lithostratigraphic geometry may be an additional cause of strong site effects.

A WebGis tool for seismic hazard scenarios and risk analysis

The WebGis development represents a natural answer to the growing requests for dissemination and use of geographical information data. WebGis originates from a combination of web technology and the Geographical Information System, which is a recognised technology that is mainly composed of data handling tools for storage, recovery, management and analysis of spatial data. Here, we illustrate two examples of seismic hazard and risk analysis through the WebGis system in terms of architecture and content. The first presents ground shaking scenarios associated with the repetition of the earthquake that struck the Lake of Garda area (northern Italy) in 2004. The second shows data and results of a more extensive analysis of seismic risk in the western part of the Liguria region (north-western Italy) for residential buildings, strategic structures and historic architecture. The adoption of a freeware application (ALOV Map) assures easy exportability of the WebGis structures for projects dealing with natural hazard evaluation.

Geomorphological mapping and geophysical profiling for the evaluation of natural hazards in an alpine catchment

Abstract. Liechtenstein has faced an increasing number of natural hazards over recent decades: debris flows, slides, snow avalanches and floods repeatedly endanger the local infrastructure. Geomorphological field mapping and geo-electrical profiling was used to assess hazards near Malbun, a village potentially endangered by landslides, and especially debris flows. The area is located on the tectonic contacts of four different nappe slices. The bedrock consists of anhydrite and gypsum, dolomite, shale, marl, and limestone. The spatial distribution and occurrence of debris flows and slides is evaluated through a combination of geomorphological expert knowledge, and detailed visualization in a geographical information system. In a geo-database a symbol-based 1:3000 scale geomorphological map has been digitized and rectified into polygons. The polygons include information on the main geomorphological environment, the Quaternary material distribution and of geomorphological processes, which are stored in attribute tables. The spatial distribution of these attributes is then combined with geophysical information and displacement rates interpolated from benchmark measurements. On one of the landslides two geo-electrical profiles show that the distance to a potential failure plane varies between 10-20 m and that the topography of the failure plane is influenced by subterranean gypsum karst features. The displacement measurements show that this landslide actively disintegrates into minor slides and is not, therefore, a risk to the village of Malbun. The hazard zonation indicates that debris flows can pose a risk if no countermeasures are taken. Gypsum karst may locally accelerate the landslide activity. In contrast, the impact of debris flows is diminished because collapse dolines may act as sediment traps for the debris flow materials. This research illustrates how geomorphological expert knowledge can be integrated in a GIS for the evaluation of natural hazards on a detailed scale.

Modelling public risk evaluation of natural hazards: a conceptual approach

Abstract. In recent years, the dealing with natural hazards in Switzerland has shifted away from being hazard-oriented towards a risk-based approach. Decreasing societal acceptance of risk, accompanied by increasing marginal costs of protective measures and decreasing financial resources cause an optimization problem. Therefore, the new focus lies on the mitigation of the hazard's risk in accordance with economical, ecological and social considerations. This modern proceeding requires an approach in which not only technological, engineering or scientific aspects of the definition of the hazard or the computation of the risk are considered, but also the public concerns about the acceptance of these risks. These aspects of a modern risk approach enable a comprehensive assessment of the (risk) situation and, thus, sound risk management decisions. In Switzerland, however, the competent authorities suffer from a lack of decision criteria, as they don't know what risk level the public is willing to accept. Consequently, there exists a need for the authorities to know what the society thinks about risks. A formalized model that allows at least a crude simulation of the public risk evaluation could therefore be a useful tool to support effective and efficient risk mitigation measures. This paper presents a conceptual approach of such an evaluation model using perception affecting factors PAF, evaluation criteria EC and several factors without any immediate relation to the risk itself, but to the evaluating person. Finally, the decision about the acceptance Acc of a certain risk i is made by a comparison of the perceived risk Ri,perc with the acceptable risk Ri,acc.

Natural Hazard Evaluation, Perception and Adjustment

Natural Hazard Evaluation, Perception and Adjustment