Earthquake intensity assessment based on environmental effects: Principles and case studies
R. E. Tatevossian, E. A. Rogozhin, S. S. Arefiev, A. N. Ovsyuchenko, 2009. "Earthquake intensity assessment based on environmental effects: Principles and case studies", Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment, K. Reicherter, A. M. Michetti, P. G. Silva
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The comparison of intensity assessments based on macroseismic data and Earthquake Environmental Effects (EEE) is presented. Specific problems faced when assessing intensities using different types of scales are discussed. Two case studies of recent earthquakes with magnitudes MS=7.4 (Altai, 2003, and Neftegorsk, 1995) are used to illustrate the applicability of the INQUA EEE scale. The Altai earthquake was accompanied by surface faulting of c. 70 km length and up to 2 m of horizontal and 70 cm of vertical offset; secondary EEE were observed over 3000 km2. The dominant type of surface faulting during the Neftegorsk earthquake was strike-slip. The length of surface faulting was up to 46 km, maximum horizontal offset was 8.1 m, and average offset coherent with seismic moment was 3.9 m; secondary EEE were observed occasionally at considerable distance from the epicentre on wet seashore sands. Application of the INQUA scale shows the epicentral intensity of the Altai earthquake to be X degrees. Most consistent with all types of data (rupture length, maximum and average offsets) intensity assessment for the Neftegorsk earthquake which is within the X–XI degree range. Taking into account environmental effects in intensity scales is an essential requirement: it follows from the complex nature of an earthquake impact, which spans a very broad frequency range, including static deformations. The case studies illustrate that the intensity assessment of an earthquake, based only on damage to buildings, will be essentially incomplete.
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Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment
Given the tremendous toll in human lives and attendant economic losses, it is appropriate that scientists are working hard to understand better earthquakes, with the aim of forecasting and, ultimately, predicting them.
In the last decades increasing attention has been paid to the coseismic effects on the natural environment, creating a solid base of empirical data for the estimation of source parameters of strong earthquakes based on geological observations. The recently introduced INQUA scale (Environmental Seismic Intensity–ESI 2007 Scale) of macroseismic intensity clearly shows how the systematic study of earthquake surface faulting, coseismic liquefaction, tsunami deposits and other primary and secondary ground effects can be integrated with “traditional” seismological and tectonic information to provide a better understanding of the seismicity level of an area and the associated hazards. At the moment this is the only scientific means of equating the seismic records to the seismic cycle time-spans extending the seismic catalogues even to tens of thousands of years, improving future seismic hazard analyses.
This Special Publication covers some of the latest multidisciplinary work undertaken to achieve that aim. Eighteen papers from research groups from all continents address a wide range of topics related both to palaeoseismological studies and assessment of macroseismic intensity based only on the natural phenomena associated with an earthquake.