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Kumaon and Garhwal regions are the chief terrains of Uttarakhand Himalaya. The present article simulates the strong ground motion of the 2011 IndoNepal earthquake in the Kumaon region using modified semi empirical technique (MSET). Acceleration records at ten stations in the near field region have been simulated which validates well with actual records and therefore confirms the reliability of MSET. In addition, MSET has been used to simulate strong motion records of future scenario earthquakes (Mw 7.0 and Mw 8.0) in Kumaon region by assuming the earthquake location same as that of 2011 IndoNepal earthquake. Isoacceleration maps are also provided, which reveals more than 400 gal value of PGA at epicentral distances less than 25 kms for an earthquake of magnitude 8.0. The comparison of isoacceleration map of future scenario earthquake (Mw 7.0) in Kumaon region has been done with isoacceleration map of 1991 Uttarkashi earthquake (Mw 6.8) in Garhwal region which suggests distinct attenuation characteristics of these two regions. [ABSTRACT FROM AUTHOR]

In the 21st century, the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake occurred in Sichuan Province, southwestern China. These two powerful earthquakes caused huge property loss and numerous human casualties. The frequent occurrence of geological hazards (including landslides and debris flows) has brought great challenges to disaster prevention and reconstruction work in earthquake-prone areas. Combing the research method of field investigations with visual interpretation of high-resolution remote sensing images, this study investigates areas with a seismic intensity ≥VII. In the study, a systematic analysis is conducted to clarify the distribution characteristics of geological hazards in the Lushan and Wenchuan earthquake-prone areas based on statistics released by the Ministry of Land and Resources, Ministry of Water Resource, Ministry of Construction of China, and other related departments. Such a clarification was done through GIS technology with varied factor combinations. Hopefully, comparative analysis on the distribution characteristics of mountain disasters in Lushan and Wenchuan leads to determination of distribution similarities and differences in areas with a seismic intensity ≥VII. The study concludes, in a systematic manner, distribution characteristics under distinctive geomorphic conditions, geological structures, and other conditions in the study area; thus can serve as a reference for disaster prevention and demographic readjustment in areas with similar conditions, promoting harmonious development of humans and nature there. [ABSTRACT FROM AUTHOR]

Estimates of the probability that an ML 4.8 earthquake, which occurred near the southern end of the San Andreas fault on 24 March 2009, would be followed by an M 7 mainshock over the following three days vary from 0.0009 using a Gutenberg-Richter model of aftershock statistics (Reasenberg and Jones, 1989) to 0.04 using a statistical model of foreshock behavior and long-term estimates of large earthquake probabilities, including characteristic earthquakes (Agnew and Jones, 1991). I demonstrate that the disparity between the existing approaches depends on whether or not they conform to Gutenberg-Richter behavior. While Gutenberg-Richter behavior is well established over large regions, it could be violated on individual faults if they have characteristic earthquakes or over small areas if the spatial distribution of large-event nucleations is disproportional to the rate of smaller events. I develop a new form of the aftershock model that includes characteristic behavior and combines the features of both models. This new model and the older foreshock model yield the same results when given the same inputs, but the new model has the advantage of producing probabilities for events of all magnitudes, rather than just for events larger than the initial one. Compared with the aftershock model, the new model has the advantage of taking into account long-term earthquake probability models. Using consistent parameters, the probability of an M 7 mainshock on the southernmost San Andreas fault is 0.0001 for three days from long-term models and the clustering probabilities following the ML 4.8 event are 0.00035 for a Gutenberg-Richter distribution and 0.013 for a characteristic-earthquake magnitude-frequency distribution. Our decisions about the existence of characteristic earthquakes and how large earthquakes nucleate have a first-order effect on the probabilities obtained from short-term clustering models for these large events. [ABSTRACT FROM AUTHOR]

Terra Nova, 24, 52-61, 2012 Abstract We have analysed the history of seismic activity in the region of L'Aquila to compare the 2009 sequence with previous ones. Historical catalogues are exhaustive for large shocks, but not for small earthquakes and swarms. Our original compilation highlights repeated seismic sequences from 1315 ad to present. In the 20th century, at least 23 sequences affected the Abruzzi region, 8 of which were very close to L'Aquila. In previous centuries, we found evidence of at least 13 sequences around L'Aquila, with maximum magnitude ∼4 to ∼5. Only three sequences were followed by stronger shocks (1461, 1703 and 2009). However, many strong events of the region (1349, 1762, 1915, 1950) were not preceded by foreshocks. We describe here the last of these sequences (1985) showing its strong similarity with the 2009 one, except its final evolution (no large event in 1985). Our analysis suggests that seismic sequences alone cannot be considered straight forerunners of incoming strong events. [ABSTRACT FROM AUTHOR]

Abstract: We compare relocations of recent (1973–2005) and historic (1919–1972) earthquakes to geologic and geophysical (gravity, aeromagnetic, and uplift) information to determine the relationship of seismicity to crustal deformation in southeastern Alaska. Our results suggest that along strike changes in the structure of the Pacific plate may control the location of the ends of rupture zones for large earthquakes along the offshore Queen Charlotte fault system in the southern portion of the study area. There is a marked increase in background seismicity in the northern portion of the study area where the Fairweather fault begins to bend toward the northwest and crustal uplift due to glacial unloading exceeds 20mm/year. Focal mechanisms indicate that thrust and reverse mechanisms predominate in the region of maximum uplift, as might be expected by the decrease in ice sheet thickness. The diffuse nature of seismicity between the Fairweather and Denali faults in the northern study area suggests a complex interaction between plate/microplate interactions and glacial unloading, making it difficult to determine the optimal fault orientation for failure in moderate magnitude (5.5 to 6.5) earthquakes within this region. [ABSTRACT FROM AUTHOR]

Abstract: In order to evaluate the horizontal peak ground acceleration (HPGA) during earthquakes, the author studies the respective efficiency of two existing attenuation models [Mébarki, A., 2003a, Risques sismiques: aléas, vulnérabilité et aide à la décision par cartes SIG. Proceedings of International Conference on “Risks, Vulnerability and Reliability in Construction. Towards a reduction of disasters”. ISBN: 9961-891-01-5, pp. 82–97. Algiers, October 11–12, Mébarki, A., 2003b. Proposal of a parametric attenuation model and comparison with some worldwide earthquakes. VIIo Congreso Venezolano de Sismologia y Ingenieria Sísmica, Barquisimeto, Venezuela. November 12–13, (CD-ROM), Mébarki A., 2004. Modèle d''atténuation sismique: prédiction probabiliste des pics d''accélération, RFGC — Revue Française de Génie Civil, Hermès Ed., 8 (9–10), 1071–1086]. A comparative study of their performances is done in the case of 1999 Chi-Chi earthquake (Taiwan). The reported PGA (Peak Ground Accelerations) values correspond to hypocentral distances ranging from 15 up to 180 km with observed acceleration peaks ranging from (0.04 g) up to (1.16 g). The author considers two kinds of probabilistic distributions for the error model in order to describe the uncertainty and the variability that affect the values of the PGA: a Gamma distribution and a Log-normal distribution. The adopted error models assume that the variability of the PGA is such that its coefficient of variation is equal to 55% [Mébarki, A., 2003a. Risques sismiques: aléas, vulnérabilité et aide à la décision par cartes SIG. Proceedings of International Conference on “Risks, Vulnerability and Reliability in Construction. Towards a reduction of disasters”. ISBN: 9961-891-01-5, pp. 82–97. Algiers, October 11–12, Mébarki, A., 2003b. Proposal of a parametric attenuation model and comparison with some worldwide earthquakes. VIIo Congreso Venezolano de Sismologia y Ingenieria Sísmica, Barquisimeto, Venezuela. November 12–13, (CD-ROM), Mébarki, A., 2004. Modèle d''atténuation sismique: prédiction probabiliste des pics d''accélération, RFGC — Revue Française de Génie Civil, Hermès Ed., 8 (9–10), 1071–1086]. The obtained results show that both attenuation models provide adequate values of the PGA when a Gamma distribution is adopted for the error model. The attenuation models efficiency decreases slightly when a Log-normal distribution is adopted for the error model. [Copyright &y& Elsevier]

We have derived, evaluated, and compared two empirical methods for computing duration magnitude M D from 25 short-period vertical component stations of the Northern Morocco Seismic Network (NMSN). M D has been scaled to IGN (Insituto Geograpfico National, Spain) body-wave magnitude (mb IGN ), using a set of 479 shallow (less than 30 km) earthquakes recorded from March 1992 to February 2001, with 2.5 ≤ mb IGN ≤ 5.4. In the first approach: Individual Network Calibration, we determined an individual M D formula for each station. In the second approach: Global Network Calibration, we used a single relationship to compute M Dij (from the jth observation for the i-th earthquake) magnitudes at 25 selected stations as: M Dij = − 0.14 +1.63 log10 (τ ij )+0.031(Δ ij)+ cSta j . Residuals ( M Dij − mb IGN ) for both techniques were thereafter deduced. Comparison between the two approaches provided the principal results: (1) The mean correlation between estimated magnitude; M Dij and reference magnitude; mb IGN is about 89.9% for the individual calibration method, and near 95% for global calibration method in which station corrections cSta j were introduced, (2) Residuals ( M Dij − mb IGN ) are relatively large, and are ranging between − 0.60 and 0.60 magnitude units, for the individual calibration method, whereas they vary in the range − 0.38 to 0.40, for the global calibration method with corrections; cSta j . (3) A random distribution of residuals ( M Dij − mb IGN ) is observed for each station in the case of the individual approach. Thus, the resulting average of these residuals is almost equal to zero. Using a global calibration without corrections results in negative residuals for a group stations and positive residuals for another an group indicating respectively that sites corresponding to these groups have a tendency to underestimate, or overestimate observed magnitude values. [ABSTRACT FROM AUTHOR]