Vít Kárník

Standardization of the earthquake magnitude scale

РезюмеПредлагается стандартизация шкалы магнитуд на основе следующих принципов:а)магнитуда для всех типов волн определяется на основании формулы (1);б)при определении магнитуд применяются стандартные калибровочные функции σ(Δ);в)средное значение магнитуды для одного землетрясения определается для каждого типа волн отдельно, комбинация этих значений не рекомендуется. Обсуждается направление дальнейших исследований по объективной классификации землетрясений.

The probability of occurrence of largest earthquakes in the European area

SummaryTheGumbels theory of largest values has been applied to the estimation of probability of occurrence and of return periods of largest earthquakes in the European area. For this study shallow shocks from the period 1901–1955 and from 15 earthquake zones were used. For each zone the largest magnitudes corresponding to one-year intervals were arranged in order of increasingM, grouped in classes and then the probabilitiesF(xj) were calculated. The data plotted on the probability paper fit a straight line fairly well. The extrapolated lines yield the possibility of estimating large magnitudes which will be exceeded with a given probability, e.g. 1%. Such values were compared with largest magnitudes observed during the period 1901–1955. Their return periods indicate that in most regions the largest probable shock already occurred. Following the procedure ofEpstein-Lomnitz the coefficients α and β were calculated and compared with corresponding values ofa andb of the magnitude-frequency relation.

Vulnerability and the MSK scale

Abstract Vulnerability is defined as the degree of damage (or loss) due to shaking of a given intensity. The text of the MSK macroseismic scale describing individual intensity grades determines vulnerability functions for three main categories of structures. The resulting curves are compared with the few existing examples of vulnerability curves derived for specific categories of buildings in the Caucasus and in California.

Seismic hazard estimate for a low seismicity region — Example of Bohemia

The contribution reviews basic concepts of earthquake hazard assessment for sites of nuclear power plants. Taking into account the delineation of earthquake source regions, intensity-frequency relations, upper intensity thresholdsImax and intensity attenuation curves, we determine the seismic hazard for a site in south Bohemia and calculated the quantities defining the seismic hazard, i.e. return period in years, probability of exceedance for different intensities and different periods of interest. The adopted procedure has some limitations due to the poor definition of seismogenic zones (boundaries,N(I),Imax) and lack of strong motion observations in Central Europe.

The third asymptotic distribution of largest magnitudes in the Balkan earthquake provinces

SummaryThe third asymptotic distribution of the theory of largest values is applied to sixteen earthquake provinces in the Balkan area. The model which assumes an upper magnitude limit fits the observations better than the first distribution. Graphs and tables provide estimates of return periods of largest magnitudes.

Amplitude-distance curves of surface waves at short epicentral distances (Δ<2000 km)

РезюмеИз сравнения различных опубликованных кривых амплитудB(Δ) и соотношенияB/T(Δ) вытекает, что у значенийB/T рассеяние меньше и поэтому они более удобные для определенияM. На наклон кривых влияет преобладающий период колебаний и выделяются интервалы интерференции волн и перехода максимальной энергии с одной волновой группы на другую (Δ=100–200 км и 500–700 км). Сравнение дает возможность определить приблизительно средние калибровочные кривые дляM близких землетрясений.

The probability of occurrence of largest earthquqkes in the European area — Part II

SummaryThe previous investigation of the probability of occurrence of largest earthquakes in the European area continued by applying the Gumbel theory of largest values to three periods 1901–1930, 1901–1955 and 1901–1967, respectively. The values of magnitudes which will be exceeded with the probabilityP=1%, 2% and 10% were determined from the lines fitting the distributions of magnitudes and corresponding probabilities for all three periods. It was assumed that the relationship between the differences δMP%[k](67)=Mk,P%−M67,P% (k=30, 55, 67) and the observation period follow the hyperbolic law. This tendency was used for the estimation of the probability line corresponding to an infinite observation period.

Underground measurements of the seismic noise level

РезюмеПри помощи вертикальных сейсмографов (табл. 1, фиг. 1) в период 1959–1960 гг. было проведено несколько опытных измерений сейсмических помех в покинутых штольнях на территории Чехии (табл. 2, фиг. 2, 3). Целыо измерений была прежде всего регистрация помех в диапазонеT=0,1–2сек. Было установлено два максимума помех приT=0,5сек. иT=5сек. Амплитуды короткопериодической составляющей помех (T=0,5сек) колеблются в пределах 1–15мм в зависимости от удаления крупных промышленных центров от наблюдательного пункта. Помехи с периодомT=1сек. наблюдались лишь в исключительных случаях. Однако микросейсмы были обнаружены уже начиная с периодаT=2сек.

Seismotectonic scheme of Central and Eastern Europe

SummaryThe distribution of earthquake foci in the crust and the upper mantle indicates the position of mobile zones. Comparing epicentral maps of Central and Eastern Europe, known tectonic lines, results of deep seismic sounding and gravimetric survey enables a scheme of potential seismogenic zones, which correspond to active fault zones separating plates and blocks in the area, to be compiled. The level of earthquake activity varies along the investigated boundaries and can be considered as a measure of the intensity of the present geodynamic processes.

Isoseismal map of the Vrancea earthquake of March 4, 1977

Abstract The iaoseismal map of the intermediate Vrancea earthquake of March 4, 1977 was compiled using the contributions from many European countries within the shaken area. Characteristic features of the macroseiamic field are discussed. Mean radii of isoseismals and intensity attenuation are determined.