Probabilistic Seismic Hazard Assessment Using Legacy Data in Georgia

Abstract The Caucasus has a documented history of cataloging earthquakes stretching back to the beginning of the Christian era. Instrumental seismic observation in the Caucasus began in 1899, when the first seismograph was installed in Tbilisi, Georgia. During the Soviet era (1921–1991 in Georgia), the number of seismic stations increased in the region, providing better network coverage and a valuable dataset for seismic research. Data from many thousands of earthquakes recorded by this regional network was stored on paper in seismic bulletins. As part of the project outlined in this article, we pulled together and digitized all available paper bulletins from Georgia and neighboring countries. This allowed significant Limprovements in location accuracy and recalculation of more robust moment magnitudes for earthquakes in this region. It also paved the way for future collaboration and data exchange among the countries in the Caucasus. The resulting earthquake catalog with the new locations and magnitudes was used to conduct a probabilistic seismic hazard assessment to support a major update to the building code in Georgia to align it with the European codes. This article outlines the improvements made to the earthquake catalog in Georgia using legacy data and the new hazard assessment based on this improved dataset.

Download Full-text

Probabilistic Seismic Hazard Assessment for United Arab Emirates, Qatar and Bahrain

Applied Sciences ◽

10.3390/app10217901 ◽

2020 ◽

Vol 10 (21) ◽

pp. 7901

Author(s):

Rashad Sawires ◽

José A. Peláez ◽

Mohamed Hamdache

Keyword(s):

Seismic Hazard ◽

United Arab Emirates ◽

Hazard Assessment ◽

Return Period ◽

Seismic Hazard Assessment ◽

Probabilistic Seismic Hazard Assessment ◽

Probabilistic Seismic Hazard ◽

Earthquake Catalog ◽

Intermediate Depth ◽

Seismic Source Models

A probabilistic seismic hazard assessment in terms of peak ground acceleration (PGA) and spectral acceleration (SA) values, for both 10% and 5% probability of exceedance in 50 years, has been performed for the United Arab Emirates, Qatar, and Bahrain. To do that, an updated, unified, and Poissonian earthquake catalog (since 685 to 2019) was prepared for this work. Three alternative seismic source models were considered in a designed logic-tree framework. The discrimination between the shallow and intermediate depth seismicity along the Zagros and the Makran regions was also considered in this assessment. Three alternative ground-motion attenuation models for crustal earthquakes and one additional for intermediate-depth ones have been selected and applied in this study, considering the predominant stress regime computed previously for each defined source. This assessment highlights that the maximum obtained hazard values are observed in the northeastern part of the studied region, specifically at Ras Al-Khaimah, Umm Al-Quwain, and Fujaira, being characterized by mean PGA and SA (0.2 s) pair values equal to (0.13 g, 0.30 g), (0.12 g, 0.29 g), and (0.13 g, 0.28 g), respectively, for a 475-year return period and for B/C National Earthquake Hazards Reduction Program (NEHRP) boundary site conditions. Seismic hazard deaggregation in terms of magnitude and distance was also computed for a return period of 475 years, for ten emirates and cities, and for four different spectral periods.

Download Full-text

Probabilistic seismic hazard assessment for Hanoi city

Vietnam Journal of Earth Sciences ◽

10.15625/0866-7187/41/4/14235 ◽

2019 ◽

Vol 41 (4) ◽

pp. 321-338

Author(s):

Pham The Truyen ◽

Nguyen Hong Phuong

Keyword(s):

Seismic Hazard ◽

Hazard Assessment ◽

Seismic Hazard Assessment ◽

Probabilistic Seismic Hazard Assessment ◽

Probabilistic Seismic Hazard ◽

Earthquake Catalog ◽

Return Periods ◽

Hazard Maps ◽

Seismic Hazard Maps ◽

S Period

In this study, the methodology of probabilistic seismic hazard assessment proposed by Cornell and Esteva in 1968 was applied for Hanoi city, using an earthquake catalog updated until 2018 and a comprehensive seismotectonic model of the territory of Vietnam and adjacent sea areas. Statistical methods were applied for declustering the earthquake catalog, then the maximum likelihood method was used to estimate the parameters of the Gutenberg–Richter Law and the maximum magnitude for each seismic source zone. Two GMPEs proposed by Campbell & Bozorgnia (2008) and Akkar et al., (2014) were selected for use in hazard analysis. Results of PSHA for Hanoi city are presented in the form of probabilistic seismic hazard maps, depicting peak horizontal ground acceleration (PGA) as well as 5-hertz (0.2 sec period) and 1-hertz (1.0 sec. period) spectral accelerations (SA) with 5-percent damping on a uniform firm rock site condition, with 10%, 5%, 2% and 0,5% probability of exceedance in 50 years, corresponding to return times of 475; 975; 2,475 and 9,975 years, respectively. The results of PSHA show that, for the whole territory of Hanoi city, for all four return periods, the predicted PGA values correspond to the intensity of VII to IX degrees according to the MSK-64 scale. As for the SA maps, for all four return periods, the predicted SA values at 1.0 s period correspond to the intensity of VI to VII, while the predicted SA values at 0.2 s period correspond to the intensity of VIII to X according to the MSK-64 scale. This is the last updated version of the probabilistic seismic hazard maps of Hanoi city. The 2019 probabilistic seismic hazard maps of Hanoi city display earthquake ground motions for various probability levels and can be applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy.

Download Full-text