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We systematically investigate the identification and statistical characteristics of foreshock sequences in the North–South seismic belt (21 ~ 43°N, 97 ~ 107°E), which is the test area of China under the "Collaboratory for the Study of Earthquake Predictability (CSEP)," so as to provide data support for foreshock probability forecasting and monitoring deployment. In this paper, we use a stochastic declustering method based on a space–time epidemic-type aftershock sequence (ETAS) model to fit the real catalogs in the North–South seismic belt, and separate each catalog into stochastic versions of family trees, so as to identify the foreshock sequences and analyze their space–time characteristics and statistical characteristics. The results show that the proportion of foreshock sequences of ML ≥ 3.0 earthquakes in the North–South seismic belt is not significantly higher than that in other regions of the world (New Zealand, Southern California) without considering the difference in cutoff magnitude. The number of foreshock sequences in the North–South seismic belt displays obvious regional differences, with the number in the middle section distinctly lower and in the south section distinctly higher, while accounting for nearly 50% in all earthquake sequences except for a few areas. The foreshock sequence duration is mostly one to one hundred days, without displaying obvious correlation between the duration of sequences and foreshock sequences and latitude. The background earthquakes have a high b value, approximately 0.89. The b value of foreshock sequences, especially foreshock sequences in the strict sense, is low, approximately 0.72. The b value of aftershock sequences is the lowest, approximately 0.69. The duration of foreshocks in most earthquake sequences is lower than that of aftershocks, especially in sequences with large numbers of events. Meanwhile, sequences that last for more than 1 year have shorter foreshock sequences and longer aftershock sequences. [ABSTRACT FROM AUTHOR]

Afghanistan is a tectonically complex zone developed as a result of the collision between the Eurasian plate and the Indian plate to the southeast and the Arabian plate to the south. The active tectonics of the country is distinguished by a wide zone of crustal deformation. There is no large-scale active fault map in Afghanistan, which is essential for seismic hazard mitigation. I, therefore, mapped active and presumed active faults mainly based on interpretation of 1-arcsecond SRTM anaglyph images and shaded relief map. The map reveals that there are significant active faults across the country. In consideration based on the available data and geomorphic criteria, 22 faults are considered seismically active. The result from the mapping represents that three dominant types of structures (left-lateral strike-slip, right-lateral strike-slip, and thrust faults) characterized the interior of Afghanistan. Then the active fault map was combined with earthquake catalog data to interpret the seismic hazard and define earthquake sources based on focal mechanisms and distribution of earthquakes. To contribute to the understanding of seismic hazard, the paper outlines regions with similar neotectonic constraints and observations of type and age of faults that generate background seismicity. I delineated four seismic source zones: (1) east-northeastern, (2) Afghanistan-North Pamir, (3) Northern Afghanistan platform, and (4) middle and southwestern Afghanistan. The east-northeastern seismic zone is the most seismically active and has more crustal earthquakes in the country. This zone is cut by large active and potentially active faults, and Chaman fault is the most significant left-lateral fault that produced five historical surface ruptures. [ABSTRACT FROM AUTHOR]

This paper aims at implementing and introducing the use of conditional mean spectrum (CMS) and conditional spectrum (CS) as the main input parameters in the practice of seismic safety evaluation (SSE) in China, instead of the currently used uniform hazard spectrum (UHS). For this purpose, a procedure for M-R-epsilon seismic hazard deaggregation in China was first developed. For illustration purposes, two different typical sites in China, with one to two dominant seismic zones, were considered as examples to carry out seismic hazard deaggregation and illustrate the construction of CMS/CS. Two types of correlation coefficients were used to generate CMS and the results were compared over a vibration period range of interest. Ground motion records were selected from the NSMONS (2007-2015) and PEER NGA-West2 databases to correspond to the target CMS and CS. Hazard consistency of the spectral accelerations of the selected ground motion records was evaluated and validated by computing the annual exceedance probability rate of the response spectra and comparing the results to the hazard curve corresponding to each site of concern at different periods. The tools developed in this work and their illustrative application to specific case studies in China are a first step towards the adoption of CMS and CS into the practice of seismic safety evaluation in this country. [ABSTRACT FROM AUTHOR]

This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615-2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study—Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study undertaken to evaluate the implications of the newly mapped offshore Mount Lebanon Thrust (MLT) fault system on the seismic hazard of Lebanon and the current seismic zoning and design parameters used by the local engineering community. This re-evaluation is critical, given that the MLT is located at close proximity to the major cities and economic centers of the country. The updated seismic hazard was assessed using probabilistic methods of analysis. The potential sources of seismic activities that affect Lebanon were integrated along with any/all newly established characteristics within an updated database which includes the newly mapped fault system. The earthquake recurrence relationships of these sources were developed from instrumental seismology data, historical records, and earlier studies undertaken to evaluate the seismic hazard of neighboring countries. Maps of peak ground acceleration contours, based on 10 % probability of exceedance in 50 years (as per Uniform Building Code (UBC) 1997), as well as 0.2 and 1 s peak spectral acceleration contours, based on 2 % probability of exceedance in 50 years (as per International Building Code (IBC) 2012), were also developed. Finally, spectral charts for the main coastal cities of Beirut, Tripoli, Jounieh, Byblos, Saida, and Tyre are provided for use by designers. [ABSTRACT FROM AUTHOR]

In this paper, significant variations in rate of moderate-large earthquake occurrence during the last two centuries at the north of Persia (Alborz, Azarbaijan, and Kopeh Dagh seismotectonic provinces) were chronically investigated. Depths of some historical and instrumental earthquakes were reasonably estimated using macroseismic data. Also, empirical relationships were developed between the maximum intensity and magnitude of the earthquakes in the north of Persia. Two centuries of earthquake data (M ≥5.0) reliably demonstrates that quite periods with durations of about a few years to two decades have happened and have been subsequently followed by active periods with durations of about 10 to 70 years. The time variation of seismic hazards (achieved by the macroseismic maximum intensity, I ≥IV) almost displays a similar behavior at the study area. According to both patterns of the time variations of seismicity and the seismic hazards, it may conclude that we are within a low rate of seismic period, and we may expect a higher rate of seismicity at the Alborz in the next decades. Finally, in both the Azarbaijan and Kopeh Dagh areas, we discovered considerable migrations of the seismicity from the east to the west. [ABSTRACT FROM AUTHOR]

On October 27, 2004, a moderate size earthquake occurred in the Vrancea seismogenic region (Romania). The Vrancea seismic zone is an area of concentrated seismicity at intermediate depths beneath the bending area of the southeastern Carpathians. The 2004 M = 6 Vrancea subcrustal earthquake is the largest seismic event recorded in Romania since the 1990 earthquakes. With a maximum macroseismic intensity of VII Medvedev-Sponheuer-Kárník (MSK-64) scale, the seismic event was felt to a distance of 600 km from the epicentre. This earthquake caused no serious damage and human injuries. The main purpose of this paper is to present the macroseismic map of the earthquake based on the MSK-64 intensity scale. After the evaluation of the macroseismic effects of this earthquake, an intensity dataset has been obtained for 475 sites in the Romanian territory. Also, the maximum horizontal accelerations recorded in the area by the K2 network are compared to the intensity values. [ABSTRACT FROM AUTHOR]

The relative locations of earthquake hypocentres determined with the master-event (ME) or the double-difference (DD) methods are more accurate and less dispersive compared to the absolute locations. In this paper, we conduct synthetic tests to assess the accuracy of the ME and DD location methods, to study the effects of the control parameters on the locations and possible distortions of the foci geometry. The results indicate that the DD locations are, in general, more accurate than the ME locations and perform significantly better for large earthquake clusters due to their independence of the master event position. The location precision, however, strongly depends on the control parameters used. If the control parameters are optimally chosen, the location errors can be considerably reduced. Moreover, it is proved that no distortion such as artificial clustering of foci is introduced if relative locations are used. Finally, the efficiency of both location methods is exemplified on locations of swarm micro-earthquakes that occurred in the West Bohemia region, Czech Republic, in order to reveal a detailed geometry of the active fault zone. [ABSTRACT FROM AUTHOR]