Generation of a Stochastic Seismic Event Set Based on a New Seismicity Model in China’s Earthquake Catastrophe Model

Earthquakes are among the most devastating natural disasters in China, causing serious casualties and property losses. To effectively reduce catastrophic risk, it is important to establish an earthquake catastrophe insurance system based on the earthquake catastrophe model, of which seismic hazard analysis is a main module. Probabilistic seismic-hazard analysis uses the potential source model, seismicity model, and ground-motion attenuation model, as well as the probability method to obtain the seismic hazard value of a given point. However, because the influence of a single seismic event is required when the earthquake catastrophe model is used for risk analysis, a series of single events needs to be generated according to the potential source model so as to calculate the influence of each event on the given point. In this study, based on the seismicity model (potential sources and their seismicity parameters) used in compiling the fifth generation of Seismic Ground Motion Parameter Zoning Map of China, we use the Monte Carlo method to simulate seismic events conforming to temporal, spatial, and intensity distribution of China’s seismic activities. In the simulation process, we follow the Poisson distribution in occurrence time and the Gutenberg–Richter law in magnitude distribution, and we use potential sources and earthquake occurrence rates to describe spatial distribution. The simulated seismic events include the following parameters: date (year, month, and day), location (longitude and latitude), depth, magnitude, and attitude of seismogenic faults. The simulated seismic event set can support earthquake risk analysis in the earthquake catastrophe model and has been applied in the earthquake catastrophe model of China.

Maximum Earthquake Size and Seismicity Rate from an ETAS Model with Slip Budget

ABSTRACT We define a seismicity model based on (1) the epidemic-type aftershock sequence model that accounts for earthquake clustering, and (2) a closed slip budget at long timescale. This is achieved by not permitting an earthquake to have a seismic moment greater than the current seismic moment deficit. This causes the Gutenberg–Richter law to be modulated by a smooth upper cutoff, the location of which can be predicted from the model parameters. We investigate the various regimes of this model that more particularly include a regime in which the activity does not die off even with a vanishingly small spontaneous (i.e., background) earthquake rate and one that bears strong statistical similarities with repeating earthquake time series. Finally, this model relates the earthquake rate and the geodetic moment rate and, therefore, allows to make sense of this relationship in terms of fundamental empirical law (the Gutenberg–Richter law, the productivity law, and the Omori law) and physical parameters (seismic coupling, tectonic loading rate).

Forecasting Seismicity from Wastewater Disposal in Oklahoma

Mandated wastewater injection reductions in effect since 2016 are inadequate for preventing future, large-magnitude earthquakes in the state, according to a new induced seismicity model.

SEISMOGENIC SOURCES IN THE AEGEAN AREA AND THEIR PREDICTIVE PROPERTIES

On the basis of all available information eight circular seismogenic sources, where shallow (h 100km) earthquakes occur, are defined in the broader Aegean area. The location of each source is further improved by optimization of the quasi-periodic properties of the strong (M≥6.0) instrumentally recorded mainshocks, identified in a complete catalogue of earthquakes (1911-2014) after declustering. Moreover, in the same seismogenic sources, all M≥6.3 mainshocks that comprise another complete catalogue (1850-2014) have also occurred. Interevent times of mainshocks generated in each source have predictive properties expressed by the TIMAPR (Time and Magnitude Predictable Regional) model whereas preshocks of recent mainshocks have also such properties expressed by the D-AS (Decelerating-Accelerating Seismicity) model. Retrospective prediction of the last mainshock in each source by the joint application of the two models resulted in reasonable uncertainties. Then, as a forward test, data up to the end of 2014 were used to predict the next expected mainshock in each of the eight sources and to identify the fault where its epicentre will probably be located.

A probabilistic seismic hazard assessment of the Trans-Mexican Volcanic Belt, Mexico based on historical and instrumentally recorded seismicity

The Trans-Mexican Volcanic Belt (TMVB) is an active volcanic chain being deformed by an intra-arc extensional fault network. Although several crustal earthquakes with magnitude>7 have originated in the TMVB since the 16th century, the background seismicity of this geological structure is very low and the region is usually considered of low seismic hazard. In this study, we present an updated probabilistic seismic hazard model of the TMVB. The seismicity catalog used here includes forty-three historically and instrumentally recorded earthquakes, from 1858 to 2014; five of these are large earthquakes that occurred in the TMVB during the XIXth century. Due to the lack of a statically representative sample, we propose, in a qualitative manner, the seismicity catalog is complete for M≥4 since 1964 and for M≥6 since 1858. Moreover, we introduce three different earthquake frequency-magnitude relations. The first one is a conventional Gutenberg Richter fit of the distribution of the instrumentally recorded earthquakes data. The other two are non-conventional, semi-parametric approaches that integrate the historical and the instrumental data to determine seismicity rates in the region. Our preferred model (seismicity model B) fits separately the instrumental and the historical data and merge the two fits into one curve. A uniform seismic hazard (USH) of the TMVB for a return period of 500 years was calculated considering three major sources of earthquakes: 1) Subduction thrust-faulting events in the Middle American Trench (MAT); 2) Earthquakes within the subducted Cocos plate and, 3) Shallow crustal earthquakes in the TMVB. According to the seismicity model B, the average recurrence time of a M≥7 earthqua-ke on the TMVB is approximately 150 years. In contrast, the recurrence time estimated from the instrumental catalog is 12,000 years. The results of this seismicity model, which is based on historical and instrumental data, agrees also with the return periods of prehistoric earthquakes, estimated for short segments of the fault system in the TMVB in paleoseismological studies. When comparing the results of our preferred seismicity model, the PGA estimated using only the instrumental seismicity are 18 to 56% smaller than those predicted by the model using the historical catalog.