Abstract
In support of displacement-based design (DBD), an attenuation model for the prediction of the spectral displacement of intermediate-depth earthquakes generated by Vrancea source is proposed. DBD is an alternative to force-based design, the main benefits being a better and confident description of the structural response and the removal of some of the inconsistencies of force-based code design. The basic input for DBD is the displacement response spectrum (DRS). Vrancea intermediate-depth source is responsible for the seismic hazard for most of the Romanian territory. The source produces, on average, two or three earthquakes with MW >7.0 per century, the prominent characteristics being the large displacement demand and large predominant periods (≈ 1.5 s) for sites located in the Romanian Plain. The model is applicable for sites positioned in front of the South-Eastern Carpathian Arc on type B and C soils. Equations predicting spectral displacement were developed by two-stage regression analysis, using a database containing national analog records of moderate-strong earthquakes and the available digital records, of smaller earthquakes. The model was extended for periods up to 8.0 s using national digital strong motion records and Japanese high-quality digital records of earthquakes triggered by a similar seismo-tectonic environment. The model successfully reproduced observed data, for both type B and C soils and the goodness of fit was tested using methods available in literature.
Highlights
Romania is a country exposed to seismic hazard throughout its territory, a fact that is supported by historical evidence spanning more than ten centuries
This paper focuses on the main input for displacement-based design (DBD) procedure, the relative displacement spectrum, for earthquakes of intermediate-depth and sites located in front of the Carpathian Arc, corresponding to the historical regions of Moldova, Muntenia and Dobrogea
The recorded ground motions of the 4 March 1977 earthquake, which imposes the highest displacement demands, loses its share from the first set, which is reflected in the shape and spectral values generated by this model
Summary
Romania is a country exposed to seismic hazard throughout its territory, a fact that is supported by historical evidence spanning more than ten centuries. Geosciences 2020, 10, 282 that the intermediate-depth seismicity in the Vrancea area is related to the dipping of a portion of a tectonic plate into the mantle (asthenosphere). This would be the last stage of the subduction process. At least one major event (4 March 1977, MW = 7.4) was a multi-shock source, with a foreshock and a subsequent three shocks generated within a 20-s time interval This feature is in agreement with a large release of energy over the surface of the rupture with local asperities or stress field non-uniformities. This paper focuses on the main input for DBD procedure, the relative displacement spectrum, for earthquakes of intermediate-depth and sites located in front of the Carpathian Arc, corresponding to the historical regions of Moldova, Muntenia and Dobrogea
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