Site Specific Probabilistic Seismic Hazard Model for Isfahan, Iran: Estimates and Uncertainties

Abstract We present a seismic source characterization model for the probabilistic seismic hazard assessment (PSHA) of the Isfahan urban area, Iran. We compiled the required datasets including the earthquake catalogue and the geological and seismotectonic structure and faults systems within the study region to delineate and characterize seismic source models. We identified seven relatively large zones that bound each region with similar seismotectonic characteristics and catalogue completeness periods. These regions were used for calculating the b-value of the Gutenberg-Richter magnitude recurrence relationship and for estimating the maximum magnitude value within each region. The recurrence parameters were then used to build a spatially varying distributed seismic source model using a smoothed kernel. Additionally, based on a fault database developed in this study and on a local expert’s opinion about their slip velocity, an active faults based model is also created. We further performed sets of sensitivity analyses to find stable estimates of the ground motion intensity and to define alternative branches for both the seismogenic source and ground motion prediction models. Site amplification is considered based on a Vs30 map for Isfahan compiled within this study. The alternative source and ground motion prediction models considered in the logic tree of this study are then implemented in the software Open Quake to generate hazard maps and uniform hazard spectra for return periods of interest. Finally, we provide a detailed comparison of the PSHA outcomes of the current study both with those presented in the 2014 Earthquake Model of Middle East (EMME14) and with the national seismic design spectrum to further discuss the discrepancies between hazard estimates from site-specific and regional PSHA studies.

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Site-specific seismic hazard levels at the economic zone of Duqm, Oman

Journal of Geophysics and Engineering ◽

10.1093/jge/gxab050 ◽

2021 ◽

Vol 18 (5) ◽

pp. 740-760

Author(s):

Ahmed Deif ◽

Adel M E Mohamed ◽

Issa El-Hussain ◽

Yousuf Al-Shijbi ◽

Sherif El-Hady ◽

...

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Return Period ◽

Hazard Evaluation ◽

Motion Prediction ◽

Soil Parameters ◽

Maximum Magnitude ◽

Ground Motion Prediction ◽

Site Specific ◽

Economic Zone

Abstract A site-specific probabilistic seismic hazard assessment (PSHA) was achieved in the area of special economic zone authority of Duqm, involving hazard evaluation at the bedrock conditions and assurance of potential site influence on seismic ground motion at the bedrock. Appropriate source and ground-motion prediction models were selected and seismic hazards were identified by means of 5% damped Uniform Hazard Spectra (UHS) for three return periods of 475, 975, and 2475 years. A logic-tree algorithm was used to study the influence of the epistemic uncertainties on the source models, earthquake recurrency and maximum magnitude, along with ground-motion prediction equations (GMPEs). The local geology effects were characterized by fundamental resonance frequency (Fo) using the horizontal-to-vertical spectral ratio technique and the soil amplification factors. The effects of soil were assessed using SHAKE91 for soil parameters defined by 55 geotechnical boreholes in conjunction with surveys of 2D multichannel analysis of surface waves (MASW) at 90 sites. Scaling was performed for selected strong-motion applying spectral matching technique to be used at the soil column bottom. Selection of such records is based on scenarios characterized by deaggregation of the PSHA results on the bedrock tops. The Duqm area mostly features low amplifications, below 1.3 for the considered spectrum. Surface ground-motion maps show low hazard values with Peak Ground Accelerations (PGA) vary between about 2 and 5% g for a 475-year return period. Although several sites are assessed to be susceptible to liquefy, liquefaction analyses indicate that surface ground motions for a 475-year return period are insufficient to produce liquefaction.

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On the Forecasting of Ground-Motion Parameters for Probabilistic Seismic Hazard Analysis

Earthquake Spectra ◽

10.1193/1.3525379 ◽

2011 ◽

Vol 27 (1) ◽

pp. 1-21 ◽

Cited By ~ 14

Author(s):

Danny Arroyo ◽

Mario Ordaz

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Prediction Models ◽

Hazard Analysis ◽

Probabilistic Seismic Hazard Analysis ◽

Seismic Hazard Analysis ◽

Motion Prediction ◽

Probabilistic Seismic Hazard ◽

Ground Motion Prediction ◽

Data Set

It is well understood that the range of application for an empirical ground-motion prediction model is constrained by the range of predictor variables covered in the data used in the analysis. However, in probabilistic seismic hazard analysis (PSHA), the limits in the application of ground-motion prediction models (GMPMs) are often ignored, and the empirical relationships are extrapolated. In this paper, we show that this extrapolation leads to a quantifiable increment in the uncertainty of a GMPM when it is used to forecast a future value of a given intensity parameter. This increment, which is clearly of epistemic nature, depends on the adopted functional form, on the covariance matrix of the regression coefficients, on the used regression technique, and on the quality of the data set. In addition, through some examples using the database of the Next Generation of Ground-Motion Attenuation Models project and some currently favored functional forms we study the increment in the seismic hazard produced by the extrapolation of GMPMs.

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Probabilistic seismic hazard assessment for Taiwan: TEM PSHA2020

Earthquake Spectra ◽

10.1177/8755293020951587 ◽

2020 ◽

Vol 36 (1_suppl) ◽

pp. 137-159

Author(s):

Chung-Han Chan ◽

Kuo-Fong Ma ◽

J Bruce H Shyu ◽

Ya-Ting Lee ◽

Yu-Ju Wang ◽

...

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Seismic Hazard Assessment ◽

Site Amplification ◽

Motion Prediction ◽

Probabilistic Seismic Hazard Assessment ◽

Probabilistic Seismic Hazard ◽

Ground Motion Prediction Equations ◽

Ground Motion Prediction ◽

Seismogenic Structure

The Taiwan Earthquake Model (TEM) published the first version of the Taiwan probabilistic seismic hazard assessment (named TEM PSHA2015) 5 years ago. For updating to the TEM PSHA2020, we considered an updated seismogenic structure database, including the structures newly identified with 3D geometry, an earthquake catalog made current to 2016, state-of-the-art seismic models, a new set of ground motion prediction equations, and site amplification factors. In addition to earthquakes taking place on each individual seismogenic structure, the updated seismic model included the possibility of an earthquake occurring on multiple structures. To include fault memory for illustrating activity on seismogenic structure sources, we incorporated the Brownian passage time model. For the crustal seismicity that cannot be attributed to any specific structure, we implemented both area source and smoothing kernel models. A new set of ground motion prediction equations is incorporated. In addition to the calculation of hazard at engineering bedrock, our assessment included site amplification factors that competent authorities of governments and private companies could use to implement hazard prevention and reduction strategies.

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