Seismic Hazard Values Research Articles

Seismic hazard assessment in Aswan, Egypt

The study of earthquake activity and seismic hazard assessment around Aswan is very important due to the proximity of the Aswan High Dam. The Aswan High Dam is based on hard Precambrian bedrock and is considered to be the most important project in Egypt from the social, agricultural and electrical energy production points of view. The seismotectonic settings around Aswan strongly suggest that medium to large earthquakes are possible, particularly along the Kalabsha, Seiyal and Khor El-Ramla faults. The seismic hazard for Aswan is calculated utilizing the probabilistic approach within a logic-tree framework. Alternative seismogenic models and ground motion scaling relationships are selected to account for the epistemic uncertainty. Seismic hazard values on rock were calculated to create contour maps for eight ground motion spectral periods and for a return period of 475 years, which is deemed appropriate for structural design standards in the Egyptian building codes. The results were also displayed in terms of uniform hazard spectra for rock sites at the Aswan High Dam for return periods of 475 and 2475 years. In addition, the ground-motion levels are also deaggregated at the dam site, in order to provide insight into which events are the most important for hazard estimation. The peak ground acceleration ranges between 36 and 152 cm s-2 for return periods of 475 years (equivalent to 90% probability of non-exceedance in 50 years). Spectral hazard values clearly indicate that compared with countries of high seismic risk, the seismicity in the Aswan region can be described as low at most sites to moderate in the area between the Kalabsha and Seyial faults.

A WebGIS Application for Rendering Seismic Hazard Data in Italy

In 2004, on behalf of the Department of Civil Protection (DPC—Dipartimento della Protezione Civile), the Istituto Nazionale di Geofisica e Vulcanologia (INGV) released a new Italian seismic hazard map. The entire scientific process was public and transparent: an international panel of experts conducted a peer review while the work was in progress, and all the input data, the final output, and the technical documentation was published. The details of the entire process are available on a dedicated Web site (http://zonesismiche.mi.ingv.it). The new hazard map provides the expected value of horizontal peak ground acceleration (PGA) with an exceedance probability of 10% in 50 years. This elaboration was recently adopted (ordinance 3519/2006 signed by the Prime Minister) as the “reference map” for assigning municipalities to one of four seismic zones according to building-code criteria. In the building code released in 2005 (ministerial decree 14/09/2005), the seismic zone assignment criteria is the expected PGA value; for each seismic zone the code also defines a standard design spectrum anchored to a fixed PGA value allowing designers to change the anchor value of the response spectra within a 20% discretionary margin when more detailed information on the expected shaking parameters of the site of interest are available. In addition to the scientific community, local administrators and professionals, typically civil engineers and architects, use seismic hazard values. Administrators use them to define the appropriate level of protection for the regions they oversee, while professionals refer to them to provide the best compromise between building costs and safety. Following the publication of the reference map, the DPC financed the S1 project to produce a set of additional elaborations that would better describe the Italian seismic hazard. This resulted in a set of maps expressed in terms of PGA and Sa (spectral accelerations), both evaluated for different …

Updating the Probabilistic Seismic Hazard Values of Northern Algeria with the 21 May 2003 M 6.8 Algiers Earthquake Included

The occurrence of the Algiers earthquake (M 6.8) of May 21, 2003, has motivated the necessity to reassess the probabilistic seismic hazard of northern Algeria. The fact that this destructive earthquake took place in an area where there was no evidence of previous significant earthquakes, neither instrumental nor historical, strongly encourages us to review the seismic hazard map of this region. Recently, the probabilistic seismic hazard of northern Algeria was computed using the spatially smoothed seismicity methodology. The catalog used in the previous computation was updated for this review, and not only includes information until June 2003, but also considers a recent re-evaluation of several historical earthquakes. In this paper, the same methodology and seismicity models are utilized in an effort to compare this methodology against an improved and updated seismic catalog. The largest mean peak ground acceleration (PGA) values are obtained in northernmost Algeria, specifically in the central area of the Tell Atlas. These values are of the order of 0.48 g for a return period of 475 years. In the City of Algiers, the capital of Algeria, and approximately 50 km from the reported epicenter of this latest destructive earthquake, a new mean PGA value of 0.23 g is obtained for the same return period. This value is 0.07 g greater than that obtained in the previous computation. In general, we receive greater seismic hazard results in the surrounding area of Algiers, especially to the southwest. The main reason is not this recent earthquake by itself, but the significant increase in the mmax magnitude in the seismic source where the city and the epicenter are included.

Seismic hazard maps of Mexico, the Caribbean, and Central and South America

The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures due to an insufficient knowledge of existing seismic hazard and/or economic constraints. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. We have produced a suite of seismic hazard estimates for Mexico, the Caribbean, and Central and South America. One of the preliminary maps in this suite served as the basis for the Caribbean and Central and South America portion of the Global Seismic Hazard Map (GSHM) published in 1999, which depicted peak ground acceleration (pga) with a 10% chance of exceedance in 50 years for rock sites. Herein we present maps depicting pga and 0.2 and 1.0 s spectral accelerations (SA) with 50%, 10%, and 2% chances of exceedance in 50 years for rock sites. The seismicity catalog used in the generation of these maps adds 3 more years of data to those used to calculate the GSH Map. Different attenuation functions (consistent with those used to calculate the U.S. and Canadian maps) were used as well. These nine maps are designed to assist in global risk mitigation by providing a general seismic hazard framework and serving as a resource for any national or regional agency to help focus further detailed studies required for regional/local needs. The largest seismic hazard values in Mexico, the Caribbean, and Central and South America generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes. High hazard values occur in areas where shallow-to-intermediate seismicity occurs frequently.

The GSHAP Global Seismic Hazard Map

Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The Global Seismic Hazard Assessment Program (GSHAP) was designed to assist in global risk mitigation by providing a useful global seismic hazard framework and by serving as a resource for any national or regional agency for further detailed studies applicable to their needs. GSHAP was launched in 1992 by the International Lithosphere Program (ILP) with the support of the International Council of Scientific Unions (ICSU) and endorsed as a demonstration program in the framework of the United Nations International Decade for Natural Disaster Reduction (UN/IDNDR). GSHAP promoted a regionally coordinated, homogeneous approach to seismic hazard evaluation, including the production and distribution of the Global Seismic Hazard Map (GSH Map), a special issue of Annali di Geofisica (December 1999) describing the map and project, and a Web site (http://seismo.ethz.ch/GSHAP/) containing regional reports, GSHAP yearly reports, summaries, and maps of seismicity, source zones, and seismic hazard values. The GSHAP strategy was to establish a mosaic of regions under the coordination of regional centers (Figure 1). The goal in the first implementation phase (1993-1995) was to establish for each region or test area a working group of national experts covering the different fields required for seismic hazard assessment, to produce common regional earthquake catalogs and databases, and to assess the regional seismic hazard. The second phase (1995-1998) of GSHAP involved expansion of these regional efforts to …

New map lays out global seismic hazard values

The first‐ever quantitative Global Seismic Hazard Map, issued on December 16, provides updated seismic hazard values for nearly half of the world's nations. The map also adjusts hazard values along some politically charged international boundaries where different methods for determining seismicity had led to dissimilar values on either side of a border.Eight percent of Earth's land mass falls within a range of high or very high seismic hazard zones on the map. That hazard is defined as a 10% or greater probability of violent shaking— which is 25% or more acceleration of gravity— within the next 50 years. About 70% of the land mass lies in a low hazard range.

A Monte Carlo approach to seismic hazard analysis

AbstractWe have developed a Monte Carlo methodology for the estimation of seismic hazard at a site or across an area. This method uses a multitudinous resampling of an earthquake catalog, perhaps supplemented by parametric models, to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found. Large earthquakes extrapolated from a Gutenberg-Richter recurrence relation and characteristic earthquakes can be included in the analysis. For the ground motion attenuation with distance, the method can use either a set of observed ground motion observations from which estimates are randomly selected, a table of ground motion values as a function of epicentral distance and magnitude, or a parametric ground motion attenuation relation. The method has been tested for sites in New England using an earthquake catalog for the northeastern United States and southeastern Canada, and it yields reasonable ground motions at standard seismic hazard values. This is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance. The hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used, and the uncertainty in the ground motions increases with decreasing hazard probability. The program gives peak accelerations that are comparable to those of the 1996 U.S. national seismic hazard maps. The method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters.

Seismic hazard map of the western hemisphere

Vulnerability to natural disasters increases with urbanization and development of associated support systems (reservoirs, power plants, etc.). Catastrophic earthquakes account for 60% of worldwide casualties associated with natural disasters. Economic damage from earthquakes is increasing, even in technologically advanced countries with some level of seismic zonation, as shown by the 1989 Loma Prieta, CA ($ 6 billion), 1994 Northridge, CA ($ 25 billion), and 1995 Kobe, Japan (> $ 100 billion) earthquakes. The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures, due to an insufficient knowledge of existing seismic hazard. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of the Americas is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful global seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years for the western hemisphere. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the horizontal force a building should be able to withstand during an earthquake. This seismic hazard map of the Americas depicts the likely level of short-period ground motion from earthquakes in a fifty-year window. Short-period ground motions effect short-period structures (e.g., one-to-two story buildings). The largest seismic hazard values in the western hemisphere generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes. Although the largest earthquakes ever recorded are the 1960 Chile and 1964 Alaska subduction zone earthquakes, the largest seismic hazard (PGA) value in the Americas is in Southern California (U.S.), along the San Andreas fault.

Seismic hazard map of North and Central America and the Caribbean

Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of North and Central America and the Caribbean is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful regional seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the horizontal force a building should be able to withstand during an earthquake. This seismic hazard map of North and Central America and the Caribbean depicts the likely level of short-period ground motion from earthquakes in a fifty-year window. Short-period ground motions effect short-period structures (e.g., one-to-two story buildings). The highest seismic hazard values in the region generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes.

Application of inelastic response spectra derived from seismic hazard spectral ordinates for Canada: Discussion

In Fig. 3 of the paper, the authors have produced the mean strength reduction factors (R) for a range of target ductility values as a function of period, T (s), and they have noted that the use of elastic spectra with reduction factor involves considerable uncertainty. Because of this uncertainty, the authors prefer to obtain the design strength directly from inelastic response spectra corresponding to a range of values of the ductility (μ). The factor R may be considered as the ratio of the elastic spectral acceleration for a given period to the corresponding inelastic spectral acceleration associated with a specified inelastic damage level or ductility. The authors have used spectral curves for two different suites of records (one for high a/v ratio and the other for intermediate a/v ratio), scaled appropriately to derive two mean elastic response spectra to match reasonably with the target spectra. The same suites of record are then used to derive the inelastic response spectra for six different values of ductility. For use in the design code, curves are fitted to the inelastic spectra. The curve fitting parameters are given in Table 5. These parameters are then used in conjunction with eqs. [4] and [5] to calculate the elastic ( μ= 1) and inelastic (μ > 1) base shear values. The authors have used the spectral curves produced for the reference ground condition (RGC) described as “firm ground” in the GSC document (Adams et al. 1996). In this document, the seismic hazard values obtained for hard rock are amplified

Induced seismicity around Aswan Lake

The study of earthquake activity and seismic hazard assessment of Egypt is very important due to the great and rapid spreading of large investments in national projects, especially the nuclear power plant that will be held in the northern part of Egypt. Although Egypt is characterized by low seismicity, it has experienced occurring of damaging earthquake effect through its history. The seismotectonic sitting of Egypt suggests that large earthquakes are possible particularly along the Gulf of Aqaba–Dead Sea transform, the Subduction zone along the Hellenic and Cyprean Arcs, and the Northern Red Sea triple junction point. In addition some inland significant sources at Aswan, Dahshour, and Cairo-Suez District should be considered. The seismic hazard for Egypt is calculated utilizing a probabilistic approach (for a grid of 0.5° × 0.5°) within a logic-tree framework. Alternative seismogenic models and ground motion scaling relationships are selected to account for the epistemic uncertainty. Seismic hazard values on rock were calculated to create contour maps for four ground motion spectral periods and for different return periods. In addition, the uniform hazard spectra for rock sites for different 25 periods, and the probabilistic hazard curves for Cairo, and Alexandria cities are graphed. The peak ground acceleration (PGA) values were found close to the Gulf of Aqaba and it was about 220 gal for 475 year return period. While the lowest (PGA) values were detected in the western part of the western desert and it is less than 25 gal.