Estimating of the b-Value Based on the Characteristic Earthquake Model

[Formula: see text]-value of the Gutenberg–Richter relation as an earthquake precursor depends on the tectonic setting features. This paper presents an alternative method to calculate [Formula: see text]-value in the presence of characteristic earthquakes. The proposed equation is based on the maximum likelihood method applied on the probability density function of the characteristic earthquake model. Data from real and simulated catalogs were used to evaluate the accuracy of the proposed model. For this purpose, 224 seismic event catalogs with various properties including catalogs’ sample size, the ratios of characteristic earthquakes number to catalog’s sample size [Formula: see text] and different magnitude of characteristic earthquakes were simulated. According to the estimated [Formula: see text]-values, the earthquake occurrence probability was calculated and discussed. The results indicate that the proposed method of estimation for [Formula: see text]-value has more adaptable consideration of the characteristic earthquake behavior.

Urban Seismic Risk Assessment by Integrating Direct Economic Loss and Loss of Statistical Life: An Empirical Study in Xiamen, China

The growing densities of human and economic activities in cities lead to more severe consequences when a catastrophe such as an earthquake occurs. This study on urban seismic risk evaluation is carried out from the perspective of the direct loss caused by disasters in urban areas, including the measurement of both the expected direct economic loss and loss of life in the face of characteristic earthquakes. Aiming to estimate, quantify and visualize the earthquake risk in each unit of urban space, this research proposes to assess urban seismic risk by integrating the direct economic loss and the loss of statistical life in a disaster, with consideration of diverse earthquake frequencies. Empirical research of the proposed assessment framework and corresponding models is then conducted to measure urban seismic risk in Xiamen, China. Key findings of the case study include the expected direct economic losses and the expected number of deaths in three characteristic earthquakes, their estimated spatial distributions, the average loss of the value of a statistical life (VSL) of one average local resident and the overall seismic risk distributions in Xiamen.

Risk-targeted alternatives to deterministic ground motion caps in U.S. seismic provisions

Since their inception over 20 years ago, the maximum considered earthquake ground motion maps in U.S. building codes have capped probabilistic values with deterministic ground motions from characteristic earthquakes on known active faults. This practice has increasingly been called into question both because of spatially non-uniform risk levels that are produced (risk being higher mainly in coastal California) and practical difficulties in defining characteristic earthquakes from recent earthquake rupture forecast models. We describe two proposals developed to enable phase-out of deterministic caps. One approach modestly increases collapse risk targets nationwide based on recent information on return periods of characteristic earthquakes on major central and eastern U.S. seismic sources; adoption of this approach would remove the perceived need for caps in California. The second approach uses geographically varying collapse risk targets, being higher near the highly active faults in California and unchanged elsewhere. Neither approach was adopted for the 2020 National Earthquake Hazards Reduction Program recommended seismic Provisions for new building structures, but they are described in a Part 3 document to accompany the Provisions and Commentary.

A non-stationary earthquake probability assessment with the Mohr–Coulomb failure criterion

From theory to experience, earthquake probability associated with an active fault should be gradually increasing with time since the last event. In this paper, a new non-stationary earthquake assessment motivated/derived from the Mohr–Coulomb failure criterion is introduced. Different from other non-stationary earthquake analyses, the new model can more clearly define and calculate the stress states between two characteristic earthquakes. In addition to the model development and the algorithms, this paper also presents an example calculation to help explain and validate the new model. On the condition of best-estimate model parameters, the example calculation shows a 7.6 % probability for the Meishan fault in central Taiwan to induce a major earthquake in years 2015–2025, and if the earthquake does not occur by 2025, the earthquake probability will increase to 8 % in 2025–2035, which validates the new model that can calculate non-stationary earthquake probability as it should vary with time.