Probabilistic seismic hazard assessment of Kazakhstan and Almaty city in peak ground accelerations

As for many post-soviet countries, Kazakhstan’s building code for seismic design was based on a deterministic approach. Recently, Kazakhstan seismologists are engaged to adapt the PSHA(probabilistic hazard assessment) procedure to the large amount of available geological, geophysical and tectonic Kazakh data and to meet standard requirements for the Eurocode 8. The new procedure has been used within National projects to develop the Probabilistic GSZ(General Seismic Zoning) maps of the Kazakhstan territory and the SMZ(Probabilistic Seismic Microzoning) maps of Almaty city. They agree with the seismic design principles of Eurocode 8 and are expressed in terms of not only seismic intensity,but also engineering parameters(peak ground acceleration PGA). The whole packet of maps has been developed by the Institute of Seismology, together with other Kazakhstan Institutions. Our group was responsible for making analysis in PGA. The GSZ maps and hazard assessment maps for SMZ in terms of PGA for return periods 475 and 2475 years are considered in the article.

Local seismic hazard map based on the response spectra of stiff and very dense soils in Bengkulu city,Indonesia

It is well known that seismic hazard assessment should be implemented to design infrastructures in an earthquake-prone area such as Bengkulu.This paper presents local seismic hazard maps based on the response spectra of stiff and very dense soils in Bengkulu city,Indonesia.We collect the soil data and conduct the seismic wave propagation.The input motion for wave propagation analysis is generated from the spectral acceleration curves of stiff and dense soils.Various ground motion parameters such as peak ground acceleration,short-period and long-period spectral accelerations,and amplification factors are presented in microzonation maps.The results show that the peak ground acceleration in the study area ranges from 0.2 to 0.8 g,while the spectral acceleration varies between 0.5-1.5 g and 0.4-0.8 g for periods of 0.2 and 1 s,respectively.The amplification factor of the site is observed to vary from 0.5 to 1.6.Considering other spectral accelerations in Bengkulu,the spectral acceleration design shows a good performance.The results indicate the site characteristics of Bengkulu city,which can provide engineers with site class for structural building design.

Seismic Hazard Assessment for Japan after the 2011 Tohoku-Oki Mega-Thrust Earthquake （Mw9.0）

The Tohoku-Oki earthquake （Mw 9.0） of March 11,2011, was the largest event in the history of Japan. This magnitude 9.0 mega-thrust earthquake initiated approximately 100 km off-shore of Miyagi prefecture and the rupture extended 400-500 km along the Pacific plate. Due to the strong ground motions and tsunami associated by this event, approximately twenty thousand people were killed or missing and more than 220 thousands houses and buildings were totally or partially destroyed. This mega-thrust earthquake was not considered in the national seismic hazard maps for Japan that was published by the HERP （headquarters for earthquake research promotion） of Japan. By comparing the results of the seismic hazard assessment and observed strong ground motions, we understand that the results of assessment were underestimated in Fukushima prefecture and northern part of Ibaraki prefecture. Its cause primarily lies in that it failed to evaluate the Mw 9.0 mega-thrust earthquake in the long-term evaluation for seismic activities. On the other hand, another cause is that we could not make the functional framework which is prepared for treatment of uncertainty for probabilistic seismic hazard assessment work fully. Based on the lessons learned from this earthquake disaster and the experience that we have engaged in the seismic hazard mapping project of Japan, we consider problems and issues to be resolved for probabilistic seismic hazard assessment and make new proposals to improve probabilistic seismic hazard assessment for Japan.

Mapping Seismic Hazard for Canadian Sites Using Spatially Smoothed Seismicity Model

The estimated seismic hazard based on the delineated seismic source model is used as the basis to assign the seismic design loads in Canadian structural design codes.An alternative for the estimation is based on a spatially smoothed source model.However,a quantification of differences in the Canadian seismic hazard maps(CanSHMs)obtained based on the delineated seismic source model and spatially smoothed model is unavailable.The quantification is valuable to identify epistemic uncertainty in the estimated seismic hazard and the degree of uncertainty in the CanSHMs.In the present study,we developed seismic source models using spatial smoothing and historical earthquake catalogue.We quantified the differences in the estimated Canadian seismic hazard by considering the delineated source model and spatially smoothed source models.For the development of the spatially smoothed seismic source models,we considered spatial kernel smoothing techniques with or without adaptive bandwidth.The results indicate that the use of the delineated seismic source model could lead to under or over-estimation of the seismic hazard as compared to those estimated based on spatially smoothed seismic source models.This suggests that an epistemic uncertainty caused by the seismic source models should be considered to map the seismic hazard.

Disaster Investigation for August 20^th,2019 Sanya M4.2 Earthquake in Hainan,China

On August 20th,2019,a M4.2 earthquake occurred near Zhanan and Lixin Village,Tianya District,Sanya City,Hainan Province. We conduct field investigations in the vicinity of the epicenter which includes 25 natural villages based on the data provided by local government and finally complete the map of the earthquake intensity.Through the analysis of the houses and cracks in the earthquake area,the structure types and crack characteristics of the houses are basically unveiled. Furthermore,suggestions for earthquake disaster reduction in study area are obtained from the investigation.

Estimating Seismic Intensity Maps of the 2021 Mw 7.3 Madoi,Qinghai and Mw 6.1 Yangbi,Yunnan,China Earthquakes

This study focuses on rapidly determining seismic intensity maps of earthquakes because it offers fundamental information for effective emergency rescue and subsequent scientific research,and remains challenging to accurately determine seismic intensity map in regions with sparse instrumental observations.Here we applied a novel method that consisted of array technology(backprojection),ground-motion prediction equations,and site corrections,to estimate the seismic intensity maps of the 2021 Mw 7.3 Madoi,Qinghai and the Mw 6.1 Yangbi,Yunnan,China earthquakes.We used seismic data recorded at European stations to back-project the source processes of the 2021 Mw7.3 Madoi,Qinghai and the Mw 6.1 Yangbi,Yunnan,China earthquakes.The back-projected energy radiations were then used as subevents or used to define the fault geometry.Summing the contributions of each subevent or estimating the shortest distances from each site to the rupture fault,we obtained the ground motion(PGA and PGV)for each site under rock site conditions.The estimated ground motions were corrected at each site for local site amplification according to the Vs30 database.Our estimated seismic intensity maps and field reports showed high similarity,which further validated the effectiveness of the novel approach,and pushed the limit of earthquake size down to~M 6.Such efforts would substantially help in the fast and accurate evaluation of earthquake damage,and precise rescue efforts.