Earthquake Hazard Modelling and Forecasting for Disaster Risk Reduction

Adamia

Chabukiani

et al. 2020

Earth-Science Reviews

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Being a part of ongoing continental collision between the Arabian and Eurasian plates, the Caucasus region is a remarkable site of moderate to strong seismicity, where devastating earthquakes caused significant losses of lives and livelihood. In this article, we survey geology and geodynamics of the Caucasus and its surroundings; magmatism and heat flow; active tectonics and tectonic stresses caused by the collision and shortening; gravity and density models; and overview recent geodetic studies related to regional movements. The tectonic development of the Caucasus region in the Mesozoic-Cenozoic times as well as the underlying dynamics controlling its development are complicated processes. It is clear that the collision is responsible for a topographic uplift / inversion and for the formation of the fold-and-thrust belts of the Greater and Lesser Caucasus. Tectonic deformations in the region is influenced by the wedge-shaped rigid Arabian block indenting into the relatively mobile region and producing near N-S compressional stress and seismicity in the Caucasus. Regional seismicity is analysed with an attention to sub-crustal seismicity under the northern foothills of the Greater Caucasus, which origin is unclearwhether the seismicity associated with a descending oceanic crust or thinned continental crust. Recent seismic tomography studies are in favour of the detachment of a lithospheric root beneath the Lesser and Greater Caucasus. The knowledge of geodynamics, seismicity, and stress regime in the Caucasus region assists in an assessment of seismic hazard and risk. We look finally at existing gaps in the current knowledge and identify the problems, which may improve our understanding of the regional evolution, active tectonics, geodynamics, shallow and deeper seismicity, and surface manifestations of the lithosphere dynamics. Among the gaps are those related to uncertainties in regional geodynamic and tectonic evolution (e.g., continental collision and associated shortening and exhumation, lithosphere structure, deformation and strain-stress partitioning) and to the lack of comprehensive datasets (e.g., regional seismic catalogues, seismic, gravity and geodetic surveys).

Section: Seismic Hazard and Riskmentioning

confidence: 99%

Geodynamics, seismicity, and seismic hazards of the Caucasus

Adamia

Chabukiani

et al. 2020

Earth-Science Reviews

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“…Changes in any of these indicators alter the risk calculus by increasing or reducing the impacts of disaster risk on affected communities, regions, or countries. Capacity, exposure, and vulnerability patterns vary in space and time, and the geographic patterns of the indicators are unevenly distributed leading to the disproportionate impacts of disasters, especially in disadvantaged regions or countries (Ismail-Zadeh and Cutter, 2015;Ismail-Zadeh, 2018). As geohazards cannot be significantly reduced and exposure increases with economic development, major elements in disaster risk management are the reduction of vulnerability and strengthening capacity.…”

Section: Disaster Risksmentioning

confidence: 99%

“…For example, the energy released by the 2010 Chile M8.8 earthquake was by a factor of about 500 higher than that by the 2010 Haiti M7.0 earthquake. However, the damage and the death toll showed the inverse proportionality: several hundred people lost their lives in the case of the Chile earthquake versus several hundred thousand lives in the case of the Haiti earthquake resulting in a humanitarian catastrophe (Ismail-Zadeh, 2018). Earthquake disasters happen mainly because of the unwillingness of some local authorities to invest in resistant construction due to various reasons including irresponsibility, ignorance, corruption, the perceived requirement to balance the need for costs versus the increased costs of implementation, local politics, funding availability and other urgent and more politically competitive needs (Ismail-Zadeh et al, 2017).…”

Section: Why Does a Hazard Event Turn To Become A Disaster?mentioning

confidence: 99%

Science for Earthquake Risk Reduction

Journal of the Geological Society of India

2020

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Since the beginning of the 21st century the impacts of earthquakes and other geohazard-related disasters have risen rapidly: the 2004 Sumatra-Andaman earthquake and tsunamis, the 2005 Kashmir earthquake, the 2008 Wenchuan earthquake and induced landslides, the 2010 Haiti earthquake followed by a cholera outbreak, the 2011 Tohoku earthquake, tsunamis and flooding followed by the Fukushima Daiichi nuclear accident, and the 2015 Nepal earthquake and landslides (e.g., Ismail-Zadeh et al., 2014; Cutter et al., 2015). The vulnerability of our civilization to geohazard events is still growing partly due to the increase in the number of vulnerable objects and clustering of populations and infrastructure in the areas prone to geohazard events.Understanding of disaster risk comes from recent advances in natural and social sciences, engineering, and applied research. Particularly, advances in lithosphere dynamics (e.g., Cloetingh et al., 2020), based on Earth observations, analyses, and modelling, improve the understanding of hazardous event occurrences. Earthquake assessments are supported by scientific evidences from seismology, geology, geodesy, geophysics, electromagnetism, hydrology, soil science, and by models and forecasting of extreme events. Engineering and science-based technological development contribute to improvements of earthquake-resistant constructions. Studies of physical and social vulnerabilities, exposure, capacities, and resilience help in assessing disaster risk and in preparing, responding, and adapting to possible disruptions due to disasters.Meanwhile, despite the advances and knowledge accumulated, disasters continue affecting societies. Reducing disaster risks using scientific knowledge is a foundation for sustainable development (Beer and Ismail-Zadeh, 2003; Cutter et al. 2015). Our knowledge about earthquakes and their interaction with human systems is lacking in some important areas and is being challenged by the unforeseen or unknown repercussions of a rapidly changing and increasingly interdependent world (Ismail-Zadeh et al., 2017). Earthquake HazardsAlthough the majority of world greatest earthquakes occur at subduction zones (Stern, 2002), large earthquakes happen also in highly-populated continental collision or rift zones, such as the Tibet-Himalayan, Apennines, south-eastern Carpathians, and Caucasus 2012;2020) orogenic regions, the New Madrid (Braile et al., 1982) and the Kutch (Gupta et al., 2001) rift zones. According to the global risk analysis, an area inhabited by more than one billion people is estimated to undergo significant ground shaking by earthquakes for the next 50 years with probability 0.1 (Dilley et al., 2005). Tectonic stress generation (e.g.

“…Disasters influence profoundly all countries, economically well or less developed, and almost all sectors of economy (Ismail-Zadeh 2018). The vulnerability to earthquakes is growing essentially because of globalisation, concentration of people in and around earthquake-prone regions, physical and social vulnerability, and the increase in values exposed to earthquake hazards.…”

Section: Introductionmentioning

confidence: 99%

Numerical Modelling of Lithospheric Block-and-Fault Dynamics: What Did We Learn About Large Earthquake Occurrences and Their Frequency?

Soloviev

2022

Surv Geophys

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Dynamics of lithospheric plates resulting in localisation of tectonic stresses and their release in large earthquakes provides important information for seismic hazard assessments. Numerical modelling of the dynamics and earthquake simulations have been changing our view about occurrences of large earthquakes in a system of major regional faults and about the recurrence time of the earthquakes. Here, we overview quantitative models of tectonic stress generation and stress transfer, models of dynamic systems reproducing basic features of seismicity, and fault dynamics models. Then, we review the thirty-year efforts in the modelling of lithospheric block-and-fault dynamics, which allowed us to better understand how the blocks react to the plate motion, how stresses are localised and released in earthquakes, how rheological properties of fault zones exert influence on the earthquake dynamics, where large seismic events occur, and what is the recurrence time of these events. A few key factors influencing the earthquake sequences, clustering, and magnitude are identified including lithospheric plate driving forces, the geometry of fault zones, and their physical properties. We illustrate the effects of the key factors by analysing the block-and-fault dynamics models applied to several earthquake-prone regions, such as Carpathians, Caucasus, Tibet-Himalaya, and the Sunda arc, as well as to the global tectonic plate dynamics.