Seismic hazard in the Sannio-Matese area of Italy

The assessment of seismic hazard at five selected sites in the Sannio-Matese region is based on the computer program SRAMSC. Owing to the extensive historical data base for the output parameter, the MSK intensiy is chosen. The seismicity model is made up of five narrow area seismic sources. Circular or elliptical macroseismic fields are assigned to individual sources. A generalized Kövesligethy equation is used for this purpose as the attenuation relationship. The study reveals similar and a rather high hazard at the sites at Benevento, Boiano, and Melfi, which are located in the zone of highest seismic activity. At the Pomigliano and Lucera sites, the assessed hazard is much lower.     

Modeling of seismic hazard for Turkey using the recent neotectonic data

Recent developments in the neotectonic framework of Turkey introduced new tectonic elements necessitating the reconstruction of Turkey's seismic hazard map. In this regard, 14 seismic source zones were delineated. Maximum earthquake magnitudes for each seismic zones were determined using the fault rupture length approximation. Regression coefficients of the earthquake magnitude–frequency relationships for the seismic zones were compiled mostly from earlier works. Along with these data, a strong ground motion attenuation relationship developed by Joyner and Boore [Joyner, W.B., Boore, D.M., 1988. Measurement, characterization, and prediction of strong ground motion. Earthquake Engineering and Soil Dynamics, 2. Recent Advances Ground Motion Evaluation, pp. 43–102.] was utilized to model the seismic hazard for Turkey using the probabilistic approach. For the modeling, the “earthquake location uncertainty” concept was employed. A grid of 5106 points with 0.2° intervals was constituted for the area encompassed by the 25–46°E longitudes and 35–43°N latitudes. For the return periods of 100 and 475 years, the peak horizontal ground acceleration (pga) in bedrock was computed for each grid point. Isoacceleration maps for the return periods of 100 and 475 years were constructed by contouring the pga values at each node.     

Seismic hazard in mega city Kolkata, India

The damages caused by recent earthquakes in India have been a wake up call for people to take proper mitigation measures, especially the major cities that lie in the high seismic hazard zones. Kolkata City, with thick sediment deposit (∼12 km), one of the earliest cities of India, is an area of great concern as it lies over the Bengal Basin and lies at the boundary of the seismic zones III and IV of the zonation map of India. Kolkata has been affected by the 1897 Shillong earthquake, the 1906 Calcutta earthquake, and the 1964 Calcutta earthquake. An analysis on the maximum magnitude and b-value for Kolkata City region is carried out after the preparation of earthquake catalog from various sources. Based on the tectonic set-up and seismicity of the region, five seismic zones are delineated, which can pose a threat to Kolkata in the event of an earthquake. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ), and Zone 5: Shield Zone (SZ). The maximum magnitude (m _max) for Zones 1, 2, 3, 4, and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. A probability of 10% exceedance value in 50 years is used for each zone. The probabilities of occurrences of earthquakes of different magnitudes for return periods of 50 and 100 years are computed for the five seismic zones. The Peak Ground Acceleration (PGA) obtained for Kolkata City varies from 0.34 to 0.10 g.     

A deterministic seismic hazard analysis for shallow earthquakes in Greece

The maximum expected ground motion in Greece is estimated for shallow earthquakes using a deterministic seismic hazard analysis (DSHA). In order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the period 426 BC–2003, a seismogenic source model with representative focal mechanisms and a set of velocity models. Because of the discrete character of the earthquake catalogue and of errors in location of single seismic events, a smoothing algorithm is applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude. Based on the selected input parameters synthetic seismograms for an upper frequency content of 1 Hz are computed on a grid of 0.2° × 0.2°. The resultant horizontal components for displacement, velocity, acceleration and DGA (Design Ground Acceleration) are mapped. The maps which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter were compiled for a mean return period of 476 years. Therefore, in order to validate our deterministic analysis, the final results are compared with PGA estimated from the maximum observed macroseismic intensity in Greece during the period 426 BC–2003.Since the results are obtained for point sources, with the frequency content scaled with moment magnitude, some sensitivity tests are performed to assess the influence of the finite extent of fault related to large events. Sensitivity tests are also performed to investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas. The ratios and the relative differences between the results obtained using different models are mapped and their mean value computed. The results highlight the importance in the deterministic approach of using good and reliable velocity models.     

Development of spectral hazard maps for a proposed revision of the Indonesian Seismic Building Code

The need to revise the current Indonesian Seismic Hazard Map contained in Indonesian Earthquake Resistant Building Code SNI 03-1726-2002 which partially adopts the concept of UBC 1997, was driven among others by the desire to better reflect the potential larger earthquake disasters faced by the nation in the future. The much larger than maximum predicted Aceh Earthquake (M _w 9.0–9.3) of 2004, followed by the destruction observed during the 2005 Nias Earthquake (M _w 8.7) urgently underline to need to consider the new conceptual approach and technological shift shown in the transition of UBC 1997 to IBC 2006. This paper presents research works for developing spectral hazard maps for Indonesia. Some improvements in seismic hazard analysis were implemented using recent seismic records. Seismic sources were modeled by background, fault, and subduction zones by considering a truncated exponential model, pure characteristic model or both models. A logic tree method was performed to account for the epistemic uncertainty and several attenuation functions were selected. Maps of PGA and spectral accelerations for a short period (0.2 s) and for a 1-s period were then developed using a probabilistic approach. The maps will be proposed as a revision for the current seismic hazard map in the Indonesian Seismic Building Code.     

The importance of paleoseismology in seismic hazard studies for critical facilities

This paper is intended to provide a perspective on the use of paleoseismological studies in the seismic hazard assessment of critical facilities, such as dams, chemical/petrochemical facilities and nuclear power plants. In particular, the use of data obtained from paleoseismological studies for probabilistic seismic hazard analyses, when the required probabilities of exceedance are very low (e.g. 10^{− 6}–10^{− 7}) is considered. Recent revisions to the IAEA Safety Standards that provide guidance to Member States in their work related to the seismic safety of nuclear power plants are presented to illustrate the importance of this emerging discipline.     

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.     

Seismic hazard analysis for critical infrastructures in California

California is in a highly seismically active region, and structures must be designed and constructed to withstand earthquakes. Seismic hazard analysis to estimate realistic earthquake ground motions and surface fault rupture offsets is done for various mitigation measures. The best policy is to avoid constructing structures crossing seismogenic faults. Because earthquake timings are unpredictable within our current understanding, the best method is time-invariant deterministic seismic hazard analysis (DHSA) to assess effects from the largest single earthquake called Maximum Credible Earthquake (MCEs) expected from seismogenic faults. Time-dependent hazard estimates such as those arrived at through probabilistic seismic hazard analysis (PSHA) are inherently unreliable. Hazard analyses based on MCEs have been in continuous use for the design and construction of highways and bridges in California for over 30 years.

This paper presents an alternative to other methods of analysis, e.g., Abrahamson (2000) [Abrahamson, N.A., 2000. State of the practice of seismic hazard evaluation. Melbourne: proceedings of GeoEng, 2000].     

Development and application of a GIS-based tool for earthquake-induced hazard prediction

An integrated GIS-based tool (GTIS) was constructed to estimate site effects related to the earthquake hazards in the Gyeongju area of Korea. To build the GTIS for the study area, intensive site investigations and geotechnical data collections were performed and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data in accordance with the procedure developed to build the GTIS. For practical applications of the GTIS used to estimate the site effects associated with the amplification of ground motion, seismic microzoning maps of the characteristic site period and the mean shear wave velocity to a depth of 30 m were created and presented as a regional synthetic strategy addressing earthquake-induced hazards. Additionally, based on one-dimensional site response analyses, various seismic microzoning maps for short- and mid-period amplification potentials were created for the study area. Case studies of seismic microzonations in the Gyeongju area verified the usefulness of the GTIS for predicting seismic hazards in the region.     

Seismic hazard in Northern Algeria using spatially smoothed seismicity. Results for peak ground acceleration

Seismic hazard in terms of peak ground acceleration (PGA) has been evaluated in northern Algeria using spatially smoothed seismicity data. We present here a preliminary seismic zoning in northern Algeria as derived from the obtained results.Initially, we have compiled an earthquake catalog of the region taking data from several agencies. Afterwards, we have delimited seismic areas where the b and m_max parameters are different. Finally, by applying the methodology proposed by Frankel [Seismol. Res. Lett. 66 (1995) 8], and using four complete and Poissonian seismicity models, we are able to compute the seismic hazard maps in terms of PGA with 39.3% and 10% probability of exceedance in 50 years.A significant result of this work is the observation of mean PGA values of the order of 0.20 and 0.45 g, for return periods of 100 and 475 years, respectively, in the central area of the Tell Atlas.     

基于GIS的万州示范区地质灾害灾情评估系统设计

文章结合地质灾害灾情评估的特点和发展需要，提出运用地理信息系统(GIS)先进技术进行地质灾害灾情评估的框架，讨论以地理信息系统为开发平台的区域地质灾害灾情评估系统的设计。建立系统总体框架、工作流程，以及灾情评估模型的模块功能。该设计结合当前地质灾害管理、评估的需要，为区域地质灾害评估提供了一个应用例证。     

Seismic Hazard for Selected Sites in Greece: A Bayesian Estimate of Seismic Peak Ground Acceleration

A procedure for estimating maximum values of seismic peak ground accelerationat the examined site and quantiles of its probabilistic distribution in a future timeinterval of a given length is considered. The input information for the method areseismic catalog and regression relation between peak seismic acceleration at a givenpoint and magnitude and distance from the site to epicenter (seismic attenuation law).The method is based on Bayesian approach, which simply accounts for influenceof uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sitesin Greece.     

Assessment of earthquake hazard in Panama based on seismotectonic regionalization

Assessment of seismic hazard in Panama is made using a seismotectonic regionalization model. The coefficients of Gumbel's Type-I distribution are calculated and return periods for several magnitudes are found. From these coefficients intensities, peak ground acceleration and earthquake hazard for a set of return periods and epicentral distances are estimated and substantial variations in the probability of occurrence are noted. The Panama Fracture Zone (PFZ) and the Panama-South America Suture Zone (PSZ) provinces are the most active in producing earthquakes with a magnitude of about 7.0 in less than 16 yr. Magnitude 7.0 earthquakes in the Azuero province have a return period of about 160 yr, whereas in the Panama Deformed Belt (PDB) province the return period for magnitude 7.5 events is about 175 yr.     

Seismic Hazard and Risk Assessment for Tulbagh,South Africa: Part II – Assessment of Seismic Risk

This is the second part of our study on the assessment of seismic hazard and seismic risk for Tulbagh, the settlement, located about 90 km N-E from Cape Town, where the strongest and most damaging earthquake known in the existing earthquake history of South Africa took place. This part of our study, which can be read independently from Part I, concentrates on the probabilistic seismic risk analysis (PSRA) forTulbagh. The work begins with an introduction and a historical perspective on the estimation of seismic damage to buildings. The methodology for the estimation of expected damage from a probabilistic point of view is then presented. The work closes with an application of the described methodology to a site in the vicinity of Tulbagh.     

Seismic hazard in East Africa: An example of the application of incomplete and uncertain data

Earthquake hazard parameters maximum regional magnitude M _max and annual activity rate , and the b parameter of the Gutenberg-Richter relation have been evaluated for parts of East Africa. The applied maximum likelihood method permits the combination of both historical and instrumental data available (the catalog used here covers the interval 1880–1979). In addition, the uncertainty involved in magnitude determination and thresholds of completeness were taken into account. The hazard-parameter determination was performed for two study areas corresponding to segments of the eastern and western branches of the East African rift system. The results for these areas show differences that can be partly explained through the characteristics of the data.     

Seismological hazard assessment for a site in Northern Germany, an area of low seismicity

Potential sites of nuclear waste deposits in the Federal Republic of Germany are situated in areas of low seismicity. Nevertheless, seismic hazard assessment has to be performed for a very long time period in order to prove the facilities of the repositories able to withstand seismic induced loads; even though there is a considerable debate whether or not it is possible to quantify the seismic risk in such an area.

A combination of deterministic and probabilistic methods is used to assess the seismic hazard for a site in Northern Germany, fulfilling the standards of the German building code for nuclear power plants. As an example, the site of the former iron ore mine Konrad is investigated. The deterministic method is based on the assumption that the strongest earthquakes inside a tectonic region can happen everywhere there, also near the selected site. For the probabilistic method, several models describing the seismicity in an area of 200 km around the site are used to show the influence of the variability in input parameters, like the maximum intensity of each source region on the exceeding probability of the site intensity. It can be shown that the seismic hazard of a site in an area of low seismicity is mainly caused by the effects of distant but strong source regions and the background seismicity for very low probabilities.

Probabilistic evaluation has the advantage of quantifying the seismic risk. But deterministic and probabilistic methods together seem a practical tool for mutual control of the results and to overcome the weakness of each approach alone. The historical German earthquake catalog with an observation period of about 1200 years is the basis for the input data for a probabilistic model. From a deep knowledge of geological development and structural geology, the time history of the surrounding faults is developed. Indications were found that the nearest and most important fault was active at least 5 Ma ago. The combination of both seismicity and tectonics provides the basis for a long term prognostic with probabilities of exceedance in the order of 10⁻⁵ per year.

For the investigated site the following parameters were derived: site intensity as a function of exceeding probability; site acceleration; strong motion duration; site dependent response spectra for the surface and the underground inside the mine.     

基于层次分析法的绵阳市地质灾害易发性评价

文章阐述了层次分析法应用于地质灾害易发性评价过程及步骤,并运用该方法(AHP)建立地质灾害易发性综合评价的层次分析结构模型及判断矩阵,从而确定了影响地质灾害易发程度因子的权重,建立了地质灾害易发性单灾种评价及区域地质灾害易发性综合评价的数学模型.绵阳市地质灾害易发性评价应用证明,该方法比较合理、有效,具有较高的预测精度,评价结果与实际地质灾害发育区的拟合率大于90%.     

Relationships Between Fundamental Seismic Hazard Parameters for the Different Source Regions in Turkey

Turkey has been divided into eight different seismic regions taking into consideration the tectonic environments and epicenters of the earthquakes to examine relationships of the modal values (a/b), the expected maximum magnitudes (M_max) and the maximum intensities (I_max). For this purpose, the earthquakes for the time period 1900–1992 from the Global Hypocenter Data Base CD-ROM prepared by USGS, and for the time period 1993–2001 from the PDE data and IRIS data are used. Concerning the relationships developed between different magnitude scales and between surface wave magnitudes (M_S) and intensity for different source regions in Turkey, we have constructed a uniform catalog of M_S. We have estimated the values of M_max and I_max using the Gumbel III asymptotic distribution. Highest a-values are observed in the Aegean region and the lowest b-values are estimated for the North Anatolian Fault. Maximum values of a/b, M_max and I_max are related to the eastern and western part of the North Anatolian Fault and the Aegean Arc. The lowest values of all parameters are observed near the Mid Anatolian Fault system. Linear relationships have been calculated between a/b, M_max and I_max using orthogonal regression. If one of the three parameters is computed, two other parameters can be calculated empirically using these linear relationships. Hazard maps of M_max and I_max values are produced using these relationships for a grid of equally spaced points at 1°. It is observed that the maps produced empirically may be used as a measure of seismic hazard in Turkey.     

An estimate of probabilistic seismic hazard for five cities in Greece by using the parametric-historic procedure

A probabilistic procedure was applied to assess seismic hazard for the sites of five Greek cities (Athens, Heraklion, Patras, Thessaloniki and Volos) using peak ground acceleration as the hazard parameter. The methodology allows the use of either historical or instrumental data, or a combination of both. It has been developed specifically for the estimation of seismic hazard at a given site and does not require any specification of seismic sources or/and seismic zones. A new relation for the attenuation of peak ground acceleration was employed for the shallow seismicity in Greece. The computations involved the area- and site-specific parts. When assessing magnitude recurrence for the areas surrounding the five cities, the maximum magnitude, m_max, was estimated using a recently derived equation. The site-specific results were expressed as probabilities that a given peak ground acceleration value will be exceeded at least once during a time interval of 1, 50 and 100 years at the sites of the cities. They were based on the maximum peak ground acceleration values computed by assuming the occurrence of the strongest possible earthquake (of magnitude m_max) at a very short distance from the site and using the mean value obtained with the help of the attenuation law. This gave 0.24 g for Athens, 0.53 g for Heraklion (shallow) and 0.39 g Heraklion (intermediate-depth seismicity), 0.30 g for Patras, 0.35 g for Thessaloniki and 0.30 g for Volos. In addition, the probabilities of exceedance of the estimated maximum peak ground acceleration values were calculated for the sites. The standard deviation of the new Greek attenuation law demonstrates the uncertainty and large variation of predicted peak ground acceleration values.     

Seismic risk assessment of buildings in urban areas: a case study for Denizli,Turkey

This study aims to carry out a seismic risk assessment for a typical mid-size city based on building inventory from a field study. Contributions were made to existing loss estimation methods for buildings. In particular, a procedure was introduced to estimate the seismic quality of buildings using a scoring scheme for the effective parameters in seismic behavior. Denizli, a typical mid-size city in Turkey, was used as a case study. The building inventory was conducted by trained observers in a selected region of Denizli that had the potential to be damaged from expected future earthquakes according to geological and geotechnical studies. Parameters that are known to have some effect on the seismic performance of the buildings during past earthquakes were collected during the inventory studies. The inventory includes data of about 3,466 buildings on 4,226 parcels. The evaluation of inventory data provided information about the distribution of building stock according to structural system, construction year, and vertical and plan irregularities. The inventory data and the proposed procedure were used to assess the building damage, and to determine casualty and shelter needs during the M6.3 and 7.0 scenario earthquakes, representing the most probable and maximum earthquakes in Denizli, respectively. The damage assessment and loss studies showed that significant casualties and economic losses can be expected in future earthquakes. Seismic risk assessment of reinforced concrete buildings also revealed the priorities among building groups. The vulnerability in decreasing order is: (1) buildings with 6 or more stories, (2) pre-1975 constructed buildings, and (3) buildings with 3–5 stories. The future studies for evaluating and reducing seismic risk for buildings should follow this priority order. All data of inventory, damage, and loss estimates were assembled in a Geographical Information System (GIS) database.