Probabilistic Seismic Hazard Analysis Based on Arias Intensity in the North–South Seismic Belt of China

ABSTRACT Arias intensity (IA), as an important seismic parameter, which contains the information of amplitude, frequencies, and duration of ground motion, plays a crucial role in characterizing seismic hazard such as earthquake-induced landslides. In this article, we conducted probabilistic seismic hazard analysis (PSHA) based on IA in China’s north–south seismic belt. We adopted the seismic sources and seismicity parameters used in the fifth generation of the Seismic Ground Motion Parameter Zoning Map of China, and two ground-motion model of IA. The results show that the values of IA are greater than 0.11 m/s in most regions of the north–south seismic belt. The provincial capital cities and most prefecture-level cities in the seismic zone are located in the region with IA-values greater than 0.32 m/s. The values of IA are above 0.54 m/s in the region around the main fault zone. This means that the north–south seismic belt is prone to extremely high-seismic hazard, particularly earthquake-induced landslides. Therefore, it is important to strengthen the evaluation and prevention of earthquake-induced landslides in this area. As we have found significant differences in the values of IA calculated from different ground-motion model, it is necessary to study the ground-motion model of IA for the western geological environment of China. In addition, the PSHA based on IA gives more consideration to the influence of large earthquakes than that based on peak ground acceleration. Therefore, IA plays an important role in seismic design of major engineering projects. The results of this article are of great scientific significance for understanding the seismic hazard of the north–south seismic belt.

Seismic hazard and seismicity parameters in southwestern Alborz

Alborz Province is located west of Tehran Province on the South Alborz seismic belt. Geological and seismological analyses within a radius of 200 km from the center of Karaj identified five seismic zones and seven linear seismic sources. The maximum magnitude was calculated for the seismic zones using available correlations. The Kijko and Sellevoll (1992) method was used to calculate seismicity parameters, and the graphs of the return period and the probability frequency of recurrence of the earthquake magnitude in each zone were plotted for the 475-year return period. According to the calculations, the highest and lowest earthquake magnitudes of 7.6 and 6.2 were respectively obtained in Zones 1 and 4.

Contemporary deformation and earthquake hazard of the Capital Circle of China inferred from GPS Measurements

<p>The Capital Circle (CC) is a region with high risk of great damaging earthquake hazards. In our present study, by using a subset of rigorously GPS data around the North China Plain (NCP), med-small recent earthquakes data and focal mechanism of high earthquakes data covering its surrounding regions, the following major conclusions have been reached: (a) Driven by the deformation force associated with both eastward and westward motion, with respect to the NCP, of the rigid South China and the rigid Amurian block, widespread sinistral shear appear over the NCP, which results in clusters of parallel NNE-trending faults with predominant right-lateral strike-slips via bookshelf faulting within the interior of the NCP. (b) Fault plane solutions of recent earthquakes show that tectonic stress field in the NCP demonstrate overwhelming NE-ENE direction of the maximum horizontal principal stress, and that almost all great historical earthquakes in the NCP occurred along the NWW-trending Zhangjiakou-Bohai seismic belt and the NNE-trending Tangshan-Hejian-Cixian seismic belt. Additionally, We propose a simple conceptual model for inter-seismic deformation associated with the Capital Circle, which might suggest that two seismic gaps are located on the middle part of Tangshan-Hejian-Cixian fault seismic belt (Tianjin-Hejian segment) and the northeast part of Tanlu seismic belt (Anqiu segment), and constitute as, in our opinion, high risk areas prone to great earthquakes.</p>

Time–space Distribution Characteristics of the Circum-Pacific Seismic Belt Based on Multifractal Analysis

A complete scientific system of earthquake prediction has yet to be developed, and most studies on the time–space sequence of seismic activity analysis are based on existing seismic models. By applying fractal theory with the two aspects of magnitude and intensity, a new dimension is added. In this study, we applied multifractal theory to analyse data of the Circum-Pacific seismic belt, which contains multifractal spectrums such as the relation, relation, and relation. The results suggest that earthquakes in the area which we studied contain multifractal features. The study also shows that the time–space propagation characteristics of the earthquakes are affected by the internal geological structures of the region and the adjacent area.

Discreteness of the Earth's crust, energy consumption of blocks and seismicity of the European North of Russia

The article presents results of calculations of the coefficients of discreteness and energy consumption of megablocks, transblock zones and intersection nodes in the territory of the European North of Russia (the Baltic Shield and the North of the Russian Plate). Calculations of fault surface density and the crushing («blockiness») function are carried out. Analysis of the obtained parameters showed that seismically active zones and nodes of their intersection are characterized by high values of the studied parameters comparable to the values typical for the Arctic seismic belt. Thus, we can talk about the spatial connection of blocks with increased discreteness, energy saturation and surface density of the fault with the topografic position of earthquakes.

Radon concentration anomaly characteristics in the North–South seismic belt before strong earthquake

Seismic underground fluids play an important role in earthquake prediction studies and tracking. Nearly 30 years of radon concentration monitoring data at 42 observation sites in the North–South seismic belt (22°-35° N, 100°-110° E) were collected from the National Earthquake Data Center of China Earthquake Networks Center. The possible precursor anomalies of observed radon concentration in the belt before several strong earthquakes were investigated and their spatial distribution, evolution, and variation characteristics were analyzed. The results showed that radon concentration precursor anomalies before several strong earthquakes were high, and the morphological characteristics are relatively complex. The anomaly mainly shows the turning point or accelerating change of trend background change; longer anomaly durations tend to be concentrated around epicenters. The number of observation points with anomalies was positively correlated with the proximity to the epicenter; the measurement points closest to the epicenter exhibited earlier trend anomalies. The research has important practical significance and scientific value for understanding the relationship between radon concentration anomaly and strong earthquake.

A fast automatic identification method for seismic belts based on Delaunay triangulation

Earthquake prediction practice and a large number of earthquake cases show that there may be abnormal images of small earthquake belts near the epicenter before strong earthquakes occur. For a static small earthquakes spatial distribution, due to the complexity of exhaustive algorithm, the fast automatic identification method of seismic belts has not yet been realized. Visual identification is still the main method of seismic belt discrimination. Based on the Delaunay triangulation, this paper presents a fast automatic identification method of seismic belts. The effectiveness of this method is proved by a 1000 random points test and an actual example of the 4-magnitude belts before the 2005 Jiujiang M5.7 Earthquake. The results show that: (1) Using Delaunay triangulation method, we can fast get the spatial relationship between two neighboring points; (2) using the two neighboring relationships, it can automatically extend to cluster, which carries the key information of seismic belt; (3) using the technology of minimum enclosing rectangle (MER) for the identified cluster, we can get the shape and structural information of the MER, which can be called the “suspect seismic belt”; (4) after using the other restrictions to sort and filter the suspect seismic belt, we complete the identification of seismic belt; (5) the random and actual earthquakes trial calculation shows that the Delaunay triangulation method can realize a fast automatic identification of seismic belts; and (6) this automatic identification method may provide a research basis for earthquake prediction.