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Spatio-temporal analysis of main seismic hazard parameters in the Ibero-Maghreb region using an Mw homogenized catalog

Mobarki Mourad, Talbi Abdelhak

Acta Geophysica

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2022

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Vol. 70, no 3

979--1001

EN

As a step toward probabilistic seismic hazard assessment in the Ibero–Maghreb region, this study focuses on the estimation and the analysis of main seismic hazard parameters, namely the magnitude of completeness mc, the occurrence rate λ, the Gutenberg–Richter b value, and the maximum expected magnitude Mmax. The most recent earthquake catalog database has been compiled using different earthquake sources, including historical and instrumental earthquake records covering the time period 1045−2019. International Seismological Centre catalog database has been used to get the preliminary instrumental catalog covering the study region. Then, a magnitude inter-scale conversion analysis has been carried out to obtain magnitude conversion empirical laws. These later have been used to compile a homogenized catalog with all magnitudes unified to the moment magnitude Mw scale, which is quite reliably linked to fault physical parameters. The completeness magnitude has been estimated for different time periods using the maximum curvature and the entire magnitude range methods. Subsequently, the spatio-temporal variation of the completeness magnitude has been studied to better appreciate regional data quality. This analysis resulted in three complete sub-catalogs corresponding to different magnitude of completeness, namely mc=3.5, 4.5, and 5.5, starting from 1997, 1967 and 1959. The remaining seismic hazard parameters (λ, b and Mmax) were analyzed taking into account former magnitudes of completeness. Indeed, the use of incomplete data may add significant bias to seismic hazard parameters estimates. Main results are presented as spatial maps showing variation of seismic hazard parameters for different mc values. In particular, for the first time, a combined maximum magnitude–intensity map is elaborated and analyzed. The region corresponding to the largest maximum possible magnitude Mmax has been delimited as including Chelif basin and its surrounding areas west of the capital city Algiers. Mmax hotspots with values exceeding 7 have been delimitated close to Lakhdaria and Boumerdes cities east of the capital Algiers. The corresponding hotspots include the epicenter of the 1910 Mw7 and the 2003 Mw6.8 Aumale and Zemmouri earthquakes, respectively. The magnitude of completeness mc has been found to decrease significantly during the last two decades, especially in the western part. The results obtained in this study can serve as a road map for future seismic hazard studies performed on the Ibero–Maghreb region.

2

New macroseismic intensity predictive models for Turkey

Bayrak Erdem, Nas Murat, Bayrak Yusuf

Acta Geophysica

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2019

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Vol. 67, no. 6

1483--1513

EN

In this study, we propose new attenuation relations for use in possible future macroseismicity-based analyses for Turkey. The most significant difference of the new relationships is that they are specifically designed for use in the full extent of Turkey. Besides, this paper supplies an extensive macroseismic database larger than ever collected for Turkey. To this end, a modifiable MATLAB program, which is fully presented in the electronic supplement to this paper, was written to analyze the collected isoseismal maps that were first geo-rectified and then gridded by dividing them into 0.02° arrays. The epicentral distances belonging to each point intersected with the pertinent isoseism were compiled in an event-based log. Then, all subsets were merged into a single dataset, which is presented in the electronic supplement. Required strong ground motion parameters were taken from an improved earthquake catalog recently given by Kadirioğlu et al. (B Earthq Eng 1:2, 2016). For modeling the relations, the early relations were mostly selected as patterns for our candidate attenuation models. Of all candidate models, the statistically significant ones were individually tested whether or not they were able to detect the best fitting model to our database. The predicted error margins of the proposed models were compared to those of early models using data-driven statistical tests. In conclusion, considering the usability limits, the estimation capabilities of proposed relationships were found to be useful to some extent than those of the early models developed for Turkey.

3

Delineation and segmentation of the Peripienian lineament

Kozak J., Buben J., Vencovsky M.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 2

179-206

EN

Delimitation of seismic foci clustering as concerns historical earthquakes of I0 >= 6° MSK-64 on the territory of the Czech Republic and its vicinity was examined by the method of constructing smoothed mutual epicenter distances and isolines of released seismic energy. A special regional catalogue was compiled using three published earthquake source catalogues. The segmentation of the Peripienian belt was studied and discussed with the aim to assess the maximum magnitude of a possible future earthquake.

4

Earthquake hazard maps for the Czech Republic, Poland and Slovakia

Schenk V., Schenkova Z., Kottnauer P., Guterch B., Labak P.

Acta Geophysica Polonica

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2001

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Vol. 49, nr 3

287-302

EN

This paper describes cross-border earthquake hazard maps calculated in terms of macroseismic intensities and peak ground accelerations (PGA) for the Czech Republic, Poland and Slovakia (CZ-PL-SK). The study has been done in the framework of the Global Seismic Hazard Assessment Program (GSHAP). The new earthquake parametric catalogue for CZ-PL-SK was used. The catalogue represents an updated, revised and comprehensive seismicity database without boundary problems. Earthquake data have been normalized to obtain a reliable annual recurrence graph for each seismic region and the maximum expected earthquakes have been estimated. Calculated attenuation laws allowed more advanced earthquake hazard maps to be defined. Using Cornell's standard probabilistic method, the hazard maps were calculated for the return periods 475, 1000, and 5000 years. For the period of 475 years, good coincidences were found when comparing this newely calculated intensity map with that of Grunthal for Germany (D) and Austria (A); and the PGA map with the effective ground acceleration map for Austria by Lenhardt.