Journal of Seismology最新文献

In the frame of the DAMAST (Dams and Seismicity) project, we deployed a dense high-fidelity seismological real-time network to investigate in detail the spatio-temporal seismicity distribution around the Enguri high dam, situated in the greater Caucasus in western Georgia. We aim at recording the weak seismicity in a 10 km distance around the dam structure. To lower the detection threshold by reducing the ambient background noise, we installed four seismic stations in shallow (ca. 20 m) and deep boreholes. From these stations, KIT1 with a depth of ca. 250 m is the deepest seismological station in Georgia. In this paper, we characterize the seismicity recorded by the local seismic network from October 2020 to July 2022. To have a better historical picture of the seismic activity, especially since the dam construction and initial operations, re-processing of the old seismological catalogs was carried out. This required digitizing the paper-only catalog copies prior to relocation. We finally obtain a uniform catalog for the Enguri region to characterize the seismicity and start investigating its possible relationship with the exploitation of the dam reservoirs.

We use a method based on Uniform Hazard Spectrum (UHS) to compile seismic microzonation maps for the broader area of Novi Sad, a city in Serbia. The maps are intended for use in the performance-based design (PBD) of earthquake-resistant structures. At present, PBD requires the use of two sets of spectral amplitudes, one in which the structure remains linear and the other in which it may respond nonlinearly. These PBD requirements cannot be met by using only one (same) fixed-shape spectrum and scaling by peak ground acceleration alone for varying probabilities of exceedance. The alternative we present in this paper is based on UHS and describes a combined contribution from (a) seismic excitation by local earthquakes, for which region-specific attenuation equations are used, and (b) seismic excitation by large, distant earthquakes, for which different attenuation equations are used. Our maps also take into account the influences of site geology and site soil conditions in a balanced manner.

Design spectrum shape in many recent standards and codes is defined by spectral accelerations for two periods, T_s,(~0.2s) and T_{1,(~1 s)}, modified by multiplicative factors that account for the site class and strength of the ground shaking. This article draws attention to apparent discord between spectra from actual recordings at a number of stations of the national strong motion network of Turkey with the design spectra for the same location and site characteristics as given by the national seismic hazard map. We find that, for deep basins with Site Class D or E profiles, the design spectrum seems not to recognize consistently the constant velocity and longer period demand. If this conjecture is true, it may foreshadow unsafe designs for the building stock in Turkey in similar environments. Many more earthquake recordings than are currently at hand are needed to verify the applicability of using the two-point design spectrum that is embedded in the regulation. This is not a unique problem only to the Turkey Building Earthquake Regulation (TBER 2018). The recently recorded strong ground motion records from the 06 February 2023, M 7.7 and M 7.5 Kahramanmaraş, earthquakes support the conjecture of this study and provide strong evidence for a need to revise the corner periods of the design spectrum in the Regulation.