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[en] The moment-magnitude scale Msub(W) is proposed for the quantification of Vrancea earthquakes. The asperity model is found adequate to explain the observed quasi-cycles and super-cycles in the occurrence of large events. (auhtor)
[en] For the simulation of the reference ground motion, the distribution of the amplitudes over the total duration, as well as, the strong motion duration characteristics are required. The intensity function and the strong motion duration depend on various parameters, such as earthquake magnitude, crack pattern of the source, path of the propagation of seismic waves, distance to the source, local subsurface conditions. Moreover, not only the body waves, but also the contribution of the surface waves may have to be considered in some cases. Due to the randomness of the parameters involved in earthquake motions a probabilistic consideration of the problem has been conducted. The duration characteristics of both horizontal and vertical components of strong earthquake motions have been obtained. Four different kinds of deterministic intensity function have been developed. (orig./HP)
[en] Over the four-year period from 1983 to 1986, the nationwide seismic network, together with a local temporary telemetry array installed at the end of 1983, recorded roughly 100 earthquakes in the magnitude range between 0.9 and 4.2, located in northern Switzerland and the immediately adjacent region of southern Germany. Five of the earthquakes were sufficiently strong to have been clearly felt over a large area by the population. The seismic activity was concentrated mainly in the west, along a strip extending from the southern Black Forest to the Folded Jura Mountains, and in the east, in several locations between the Bodensee (Kanton Thurgau) and the Albis (Kanton Zurich). The activity was lowest in the central part of the region under study, with a total of 7 events, all having magnitudes less than 2. Contrary to most observations of seismicity in intracontinental settings throughout the rest of the world, focal depths of earthquakes are distributed throughout the earth's crust, almost reaching the depth of the crust-mantle boundary. Focal mechanisms derived from fault-plane solutions are mostly of the intermediate type between pure strike-slip and normal faulting, and are generally consistent with directions of the horizontal components of maximum and minimum compressive stresses striking roughly NW-SE and NE-SW respectively. In several cases, it was possible to apply a cross-corelation technique to the signals, to obtain highly accurate locations of hypocenters relative to a master event; in the case of six closely grouped earthquakes, located at a depth of about 23 km, the relative distribution of hypocenters coincided exactly with the orientation of one of the focal planes derived from the fault-plane solution of the master event. 17 refs., 60 figs., 10 tabs
[en] The occurence of earthquakes in Brazil, mainly in the South-eastern region, and its relationship with the geologic features has been discussed by many Authors since the beginning of this Century. It is difficult to define intraplate seismicity and to understand the actual epirogenic displacent, but the definition of the regional stability is important for enginnering purposes and have been considered through seismologic, morphotectonic and geologic criteria. (Author)
[pt]A ocorrencia de terremoto no Brasil, principalmente na regiao Sudeste, e suas relacoes com aspectos geologicos tem sido discutidas por muitos autores desde o inicio do seculo. E dificil definir sismicidade entre placas e entender o deslocamento epirogenico real, mas a definicao de estabilidade regional e importante para os propositos da engenharia e tem sido considerada atraves de criterios sismologicos, morfotectonicos e geologicos. (E.G.)
[en] Iran is one of the most seismically active areas of the world and frequently suffers from destructive earthquakes. Rare studies on anthropogenic-induced seismicity in Iran may be related to less attention to triggered events and more concern to natural origin of earthquakes. Hence, the present study as a frontier research aims to investigate the mining-induced earthquakes in Iran. For this purpose, distribution of ~ 76,000 seismic events was investigated between the years 2006 and 2013. This study considered a correlation test to investigate the possible mining triggering of the seismic events based on a network of 194 geographical pixels (1° × 1°) in ArcGIS. Results conveniently confirmed a positive meaningful relation between all earthquake events with magnitudes M > 0.5 and mining activities in Iran (R = 0.42). Detailed results confirmed that the most of earthquake swarms (at least ~ 60%) had mining-induced origin, which were spatially located in same pixels of metallic mineral mining sites. The correlation test between earthquake swarms and mining activities indicated positive and meaningful relationships in four regions of Alborz, Kopet Dag, Kerman, and Zagros, respectively (R = 0.61, 0.54, 0.51, and 0.50). Hence, aforementioned seismic regions exposed sensitive seismic responses toward mining triggering effects in Iran.
[en] A relationship between the phase characteristics and nonstationary spectrum is studied. A generation method of nonstationary earthquake ground motions using the phase characteristics is proposed. Although there are methods multiplying a different envelope function for each period range, we have two reasons for studying the generation method using the phase characteristics. One reason is that nonstationary parameters, such as a mean and a standard deviation of the phase differences, can be simplified by using the phase characteristics. Another reason is that it is desirable if the Fourier phase angles are determined based on the magnitudes and epicentral distances, since the Fourier amplitudes are currently determined in that way. The relationship between the phase characteristics and response spectrum and between the phase characteristics and nonstationary spectrum have not clarified yet. For example, although the shape of the phase difference distribution resembles that of the envelope of time series, the standard deviation of the phase difference distribution is not always an effective measure to evaluate the response spectrum. The nonstationary spectrum is defined as a response envelope of damped single-degree-of freedom (SDOF) system, although it is usually characterized by a running spectrum. (orig./HP)
[en] Functional dependencies are established for the characteristics of seismic transients recorded at various points of a studied site, which are used to propose a new approach to seismic microzonation (SMZ) that enables the creation of new SMZ maps of strong seismic motion, with due regard for dynamic parameters of recorded transients during weak earthquakes.