scholarly journals Seismic Hazard Levels in Guinea, West Africa

2021 ◽  
Author(s):  
A Irinyemi Stephen
Keyword(s):  
West Africa ◽  
Seismic Hazard ◽  
Probabilistic Approach ◽  
B Value ◽  
Seismic Sources ◽  
Return Periods ◽  
Individual Activity ◽  
Study Region ◽  
Stable Continental Region ◽  
Hazard Levels

Abstract The occurrence of seismic activities in Guinea is infrequent, although located in a stable continental region. The hazard assessment level in Guinea, West Africa was determined by a probabilistic approach for 10 sites across the region. The calculation was carried out for 10%, 2% and 0.5% probability of exceedance in 50 years using a homogenized 100-year catalogue compiled from different seismic sources; Three prediction relations, developed for Eastern and Central North America for the stable continental region; and the R-CRISIS program. The levels of hazard estimated were high in the Palaeozoic area of Guinea. A uniform b-value of 0.70 ± 0.12, and individual activity rate (λ) were calculated for the three seismic zones. The maximum PGA values estimated for the study region are 0.08 g, 0.27 g, and 0.57 g for 475, 2475 and 9975 years return periods, respectively. Finding from this study will be useful in planning for the regional infrastructure.

scholarly journals Ground-motion scenarios consistent with PSH deaggregation for Tehran, capital city of Iran

2013 ◽  
Vol 13 (3) ◽  
pp. 679-688 ◽  
Author(s):  
F. Abdi ◽  
N. Mirzaei ◽  
E. Shabani
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Capital City ◽  
Return Periods ◽  
Local Seismicity ◽  
Period Increase ◽  
Scenario Earthquakes ◽  
Acceleration Period ◽  
Ground Motion Scenarios ◽  
Hazard Levels

Abstract. This study presents the results of probabilistic seismic hazard (PSH) deaggregation for 5%-damped 0.2 and 1.0 s spectral accelerations, corresponding to mean return periods (MRPs) of 50, and 475 yr for Tehran city. The aim of this paper is to quantify the dominant events that have the most contribution on ground-motion exceedance from the above mentioned hazard levels. The scenario earthquakes are characterized by bins of magnitude (M), source-to-site distance (R), and epsilon (ε). The results reveal that for Tehran city, the hazard is mainly controlled by local seismicity. Generally, as the spectral acceleration period increase, the contribution of larger and more distant scenario earthquakes to the overall seismic hazard increase.

Probabilistic Seismic Hazard Assessment of the Kermanshah-Sanandaj Region of Western Iran

2007 ◽  
Vol 23 (1) ◽  
pp. 175-197 ◽  
Author(s):  
Elham Shabani ◽  
Noorbakhsh Mirzaei
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Eleventh Century ◽  
Probabilistic Approach ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Probabilistic Seismic Hazard Assessment ◽  
Return Periods ◽  
Ground Acceleration ◽  
Western Iran

Seismic hazard assessment and zoning of the Kermanshah-Sanandaj region in western Iran is conducted using probabilistic approach. Two maps have been prepared to indicate the earthquake hazard of the region in the form of iso-acceleration contour lines. They display a probabilistic estimate of peak ground acceleration (PGA) over bedrock for the return periods of 475 and 50 years. A uniform catalog of earthquakes containing historical and instrumental events covering the period from the eleventh century A.D. to 2003 is used. Twelve potential seismic sources are modeled as area sources in the region. Seismicity parameters are evaluated using the method in which magnitude uncertainty and incompleteness of earthquake data are considered. Seismic hazard assessment is carried out for a grid of 357 points with 0.1° intervals using the SEISRISKIII computer program for the study area encompassed by the 46–48° E longitudes and 34–36° N latitudes. This region includes the most active segments of the Zagros Main Recent Fault; among them, the Sahneh and Nahavand faults have a well-known history of intense seismic activity. PGA values for this region are estimated to be 0.35 g and 0.20 g for 475- and 50-years return periods, respectively.

scholarly journals Role of Runoff–Infiltration Partitioning and Resolved Overland Flow on Land–Atmosphere Feedbacks: A Case Study with the WRF-Hydro Coupled Modeling System for West Africa

2016 ◽  
Vol 17 (5) ◽  
pp. 1489-1516 ◽  
Author(s):  
Joel Arnault ◽  
Sven Wagner ◽  
Thomas Rummler ◽  
Benjamin Fersch ◽  
Jan Bliefernicht ◽  
...  
Keyword(s):  
West Africa ◽  
Overland Flow ◽  
River Flow ◽  
Efficiency Coefficient ◽  
Wet Season ◽  
Coupled Modeling ◽  
Study Region ◽  
Outer Domain ◽  
Terrestrial Water

Abstract The analysis of land–atmosphere feedbacks requires detailed representation of land processes in atmospheric models. The focus here is on runoff–infiltration partitioning and resolved overland flow. In the standard version of WRF, runoff–infiltration partitioning is described as a purely vertical process. In WRF-Hydro, runoff is enhanced with lateral water flows. The study region is the Sissili catchment (12 800 km2) in West Africa, and the study period is from March 2003 to February 2004. The WRF setup here includes an outer and inner domain at 10- and 2-km resolution covering the West Africa and Sissili regions, respectively. In this WRF-Hydro setup, the inner domain is coupled with a subgrid at 500-m resolution to compute overland and river flow. Model results are compared with TRMM precipitation, model tree ensemble (MTE) evapotranspiration, Climate Change Initiative (CCI) soil moisture, CRU temperature, and streamflow observation. The role of runoff–infiltration partitioning and resolved overland flow on land–atmosphere feedbacks is addressed with a sensitivity analysis of WRF results to the runoff–infiltration partitioning parameter and a comparison between WRF and WRF-Hydro results, respectively. In the outer domain, precipitation is sensitive to runoff–infiltration partitioning at the scale of the Sissili area (~100 × 100 km2), but not of area A (500 × 2500 km2). In the inner domain, where precipitation patterns are mainly prescribed by lateral boundary conditions, sensitivity is small, but additionally resolved overland flow here clearly increases infiltration and evapotranspiration at the beginning of the wet season when soils are still dry. The WRF-Hydro setup presented here shows potential for joint atmospheric and terrestrial water balance studies and reproduces observed daily discharge with a Nash–Sutcliffe model efficiency coefficient of 0.43.

Methodology for seismic risk assessment for tubular steel wind turbine towers: application to Canadian seismic environment

2011 ◽  
Vol 38 (3) ◽  
pp. 293-304 ◽  
Author(s):  
Elena Nuta ◽  
Constantin Christopoulos ◽  
Jeffrey A. Packer
Keyword(s):  
Seismic Hazard ◽  
Wind Turbine ◽  
Seismic Loading ◽  
Element Analysis ◽  
Design Spectrum ◽  
Wind Turbine Tower ◽  
Damage States ◽  
Wind Turbine Towers ◽  
Hazard Level ◽  
Hazard Levels

The seismic response of tubular steel wind turbine towers is of significant concern as they are increasingly being installed in seismic areas and design codes do not clearly address this aspect of design. The seismic hazard is hence assessed for the Canadian seismic environment using implicit finite element analysis and incremental dynamic analysis of a 1.65 MW wind turbine tower. Its behaviour under seismic excitation is evaluated, damage states are defined, and a framework is developed for determining the probability of damage of the tower at varying seismic hazard levels. Results of the implementation of this framework in two Canadian locations are presented herein, where the risk was found to be low for the seismic hazard level prescribed for buildings. However, the design of wind turbine towers is subject to change, and the design spectrum is highly uncertain. Thus, a methodology is outlined to thoroughly investigate the probability of reaching predetermined damage states under any seismic loading conditions for future considerations.

scholarly journals Bayesian probabilities for occurrence of large earthquakes in the seismogenic sources of Japan and Phillipine during the period 1998-2017

2001 ◽  
Vol 34 (4) ◽  
pp. 1619
Author(s):  
T. M. TSAPANOS ◽  
O. CH. GALANIS ◽  
S. D. MAVRIDOU ◽  
M. P. HELMl
Keyword(s):  
Seismic Hazard ◽  
Bayesian Statistics ◽  
Poisson Distribution ◽  
Bayesian Approach ◽  
Seismic Sources ◽  
Time Interval ◽  
Seismogenic Sources ◽  
The One ◽  
Large Earthquakes ◽  
The Bayesian Approach

The Bayesian statistics is adopted in 11 seismic sources of Japan and 14 of Philippine in order to estimate the probabilities of occurrence of large future earthquakes, assuming that earthquakes occurrence follows the Poisson distribution. The Bayesian approach applied represents the probability that a certain cut-off magnitude (or larger) will exceed in a given time interval of 20 years, that is 1998-2017. This cut-off magnitude is chosen the one with M=7.0 or greater. In this case we can consider these obtained probabilities as a seismic hazard presentation. More over curves are produced which present the fluctuation of the seismic hazard between these seismic sources. These graphs of varying probability are useful either for engineering or other practical purposes

Seismicity associated with 2018 and 2020 hydraulic stimulations at EGS in Helsinki, Finland, shows limited earthquake interaction: Implication for seismic hazard assessment

2021 ◽  
Author(s):  
Grzegorz Kwiatek ◽  
Maria Leonhardt ◽  
Patricia Martínez-Garzón ◽  
Matti Pentti ◽  
Marco Bohnhoff ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Energy Input ◽  
Stress Transfer ◽  
Seismic Hazard Assessment ◽  
B Value ◽  
Temporal Distance ◽  
Probabilistic Seismic Hazard Assessment ◽  
Interevent Time ◽  
Spatio Temporal

<p>In this study we investigate the statistical spatio-temporal characteristics induced seismicity associated with two stimulation campaigns performed in 2018 and 2020 in a 6.1 km deep geothermal well near Helsinki, Finland as part of the St1 Deep Heat project. We aim to find out whether the seismic activity is passively responding to injection operations, or whether we observe signatures of significant stress transfer and strong interactions between events. The former suggests stable relaxation of seismic energy proportional to hydraulic energy input, while the latter includes stress transfer as an additional source of stress perturbation, hence implying larger seismic hazard.</p><p>The selected catalogs from 2018 and 2020 stimulation contained in total 60,814 and 4,368 seismic events, respectively, recorded during and after stimulation campaigns and above the local magnitude of M -1.5. The analyzed parameters include magnitude-frequency b-value, correlation integral (c-value), fractal dimension (D-value), interevent time statistics, magnitude correlation, interevent time ratio and generalized spatio-temporal distance between earthquakes. The initial observations suggest significant time-invariance of the magnitude-frequency b-value, and increased D and c-values only at high injection rates, the latter also guiding the rate of seismicity. The seismicity covering the stimulation period neither provide signatures of magnitude correlations, nor temporal clustering or anticlustering. The interevent time statistics are generally characterized with Gamma distribution (close to Poissonian distribution), and the generalized spatio-temporal distance suggest very limited triggering (90% of the catalog was classified as background seismicity). The observable parameters suggest the seismicity passively respond to hydraulic energy input rate with little to no time delay, and the total seismic moment is proportional to total hydraulic energy input. The performed study provides the base for implementation of time-dependent probabilistic seismic hazard assessment for the site.</p>

scholarly journals Comparison between seismic and domestic risk in moderate seismic hazard prone region: the Grenoble City (France) test site

2012 ◽  
Vol 12 (2) ◽  
pp. 511-526 ◽  
Author(s):  
F. Dunand ◽  
P. Gueguen
Keyword(s):  
Seismic Hazard ◽  
Seismic Risk ◽  
Probabilistic Approach ◽  
Test Site ◽  
Local Policy ◽  
Seismic Risk Analysis ◽  
Public Authorities ◽  
Policy Makers ◽  
Risk Acceptability ◽  
Social Importance

Abstract. France has a moderate level of seismic activity, characterized by diffuse seismicity, sometimes experiencing earthquakes of a magnitude of more than 5 in the most active zones. In this seismicity context, Grenoble is a city of major economic and social importance. However, earthquakes being rare, public authorities and the decision makers are only vaguely committed to reducing seismic risk: return periods are long and local policy makers do not have much information available. Over the past 25 yr, a large number of studies have been conducted to improve our knowledge of seismic hazard in this region. One of the decision-making concerns of Grenoble's public authorities, as managers of a large number of public buildings, is to know not only the seismic-prone regions, the variability of seismic hazard due to site effects and the city's overall vulnerability, but also the level of seismic risk and exposure for the entire city, also compared to other natural or/and domestic hazards. Our seismic risk analysis uses a probabilistic approach for regional and local hazards and the vulnerability assessment of buildings. Its applicability to Grenoble offers the advantage of being based on knowledge acquired by previous projects conducted over the years. This paper aims to compare the level of seismic risk with that of other risks and to introduce the notion of risk acceptability in order to offer guidance in the management of seismic risk. This notion of acceptability, which is now part of seismic risk consideration for existing buildings in Switzerland, is relevant in moderately seismic-prone countries like France.

scholarly journals Seismic hazard maps of Peshawar District for various return periods

2020 ◽  
Vol 20 (6) ◽  
pp. 1639-1661
Author(s):  
Khalid Mahmood ◽  
Naveed Ahmad ◽  
Usman Khan ◽  
Qaiser Iqbal
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Target Location ◽  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Source Parameters ◽  
Seismic Source ◽  
Return Periods ◽  
Hazard Maps ◽  
Seismic Hazard Maps

Abstract. Probabilistic seismic hazard analysis of Peshawar District has been performed for a grid size of 0.01∘. The seismic sources for the target location are defined as the area polygon with uniform seismicity. The earthquake catalogue was developed based on the earthquake data obtained from different worldwide seismological networks and historical records. The earthquake events obtained at different magnitude scales were converted into moment magnitude using indigenous catalogue-specific regression relationships. The homogenized catalogue was subdivided into shallow crustal and deep-subduction-zone earthquake events. The seismic source parameters were obtained using the bounded Gutenberg–Richter recurrence law. Seismic hazard maps were prepared for peak horizontal acceleration at bedrock level using different ground motion attenuation relationships. The study revealed the selection of an appropriate ground motion prediction equation is crucial for defining the seismic hazard of Peshawar District. The inclusion of deep subduction earthquakes does not add significantly to the seismic hazard for design base ground motions. The seismic hazard map developed for shallow crustal earthquakes, including also the epistemic uncertainty, was in close agreement with the map given in the Building Code of Pakistan Seismic Provisions (2007) for a return period of 475 years on bedrock. The seismic hazard maps for other return periods i.e., 50, 100, 250, 475 and 2500 years, are also presented.

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