Towards a Virtual Asian-Pacific Seismological Network

Regional international cooperation in seismic data exchange and joint seismological analysis in the Asian-Pacific regions plays an important role in the reduction of earthquake disasters in these regions as well as the development of global seismology. Based on the up-to-date development of new technology and digital broadband seismology, we discussed the Asian Seismological Commission (ASC) Proposal “Asian-Pacific Seismological Data Center”. We applied the concept of virtual seismological network (Ottemoeller and Havskov, 1999) to the proposed ASC data exchange program. Based on the development of digital seismology, we introduced a concept of “modern earthquake catalogues” which include not only location parameters and magnitudes as in the conventional earthquake catalogues but also new parameters of earthquakes such as CMT, radiated energy, STF, and earthquake rupture process. We recommended a web-based regional international data exchange program between the ASC members with the purpose of forming a virtual Asian-Pacific seismological network, and the interpretation and analysis of broadband digital seismic waveforms conducted at distributed “data centers”.

Temporal-spatial Variations of Dynamic Source Parameters in the Capital Circle Region and Its Surrounding Areas before the 2006 M_S5.1 Wenan Earthquake in Hebei Province

Source spectra,corner frequency and zero frequency amplitudes in near-source conditions were measured using waveform data from 989 earthquakes with magnitudes larger than ML2.0 observed by the Beijing Digital Telemetry Seismic Network in the Capital Circle Region of China and its surrounding areas from January 2002 to June 2006 by the Brune model.Relevant formulas that were used for the calculation of dynamic source parameters include rupture radius,seismic moment,seismic energy,stress drop,and apparent stress.Scaling relations and characteristics of temporal-spatial variations of these dynamic parameters before the MS5.1 Wenan earthquake in Hebei Province that occurred on July 20,2006 were analyzed.Results show that apparent stress,stress drop,and the ratio of seismic energy to the rupture radius had relatively high values in some areas before the Wenan earthquake.These high-value concentration areas were mainly distributed in the North China Plain seismic zone.As is seen from the time curves,parameters,such as apparent stress,stress drop,and ratio of seismic energy to rupture radius underwent significant ascending processes before the Wenan earthquake,but the variation in the corner frequency showed a descending trend.This result might be related to the enhancement of stress in the North China Plain seismic zone before the earthquake.

Comparison Research on the Records of Strong-motion Seismographs and Seismographs at the Same Station

This paper uses Jin Xing( 2004,2005) and Ma Qiang's( 2003) real-time time-domain methods to simulate and compare both the broadband strong motion acceleration and velocity records measured at the same stations in the Liaoning Telemetered Digital Seismic Network. The results show that we can get actual velocity and displacement time histories by simulating broadband acceleration records. The acceleration and displacement time histories also may be obtained by simulating broadband velocity records. This indicates that strong motion observations and seismometer observations can be substituted for each other in a certain range.

Research on the Q-value, Site Response and Seismic Source Parameters in Jiangsu and Its Adjacent Areas

Based on 49 digital seismograms recorded by 73 seismic stations in the Jiangsu Telemetered Seismic Network,the paper uses Atkinson's method to calculate the inelastic attenuation coefficient of the Jiangsu area. We find that the frequency-dependent Q in the Jiangsu region is Q( f) = 272. 1·f^(0. 5575). We also use Moya's method to invert the 63 stations' site responses. The results show that the site responses of the 25 stations in Jiangsu are approximately 1 at a range between 1Hz and 20 Hz, which is consistent with their basements on rocks. The response curves of the site responses of the 14 underground stations are similar to each other. Their site responses show an amplification at low frequencies and minimization at high frequencies. The calculation of the Brune model on the waveform data of M_L≥2. 5 earthquakes from Jiangsu Digital Seismic Network between October 2010 and May 2015 in terms of seismic source parameters of 58 seismic waves shows that there are good correlations between seismic magnitude and other source parameters such as seismic moment, source radius and corner frequency, while the correlations between seismic magnitude and stress drop,and stress drop and source radius are not so good.