Analysis And Research On Shallow Earthquakes In Qinghai-Tibet Plain Recorded By Lanzhou Digital Seismic Network

In this paper, we used Lanzhou digital seismic network wideband seismic data to summary the Qinghai-Tibet Plain shallow earthquake's characteristic. Unified the example, proposed some digitized earthquake wave's processing method, specially used the seismic array processing technology recognition weak phase, improved the accuracy of the seismic phase recognition.. Offer some methods and the reference aids for daily shallow earthquakes processing and waveform seismic phase interpretation recorded in the Lanzhou digital seismic network. Calculates Q code of the shallow earthquakes occurred in the northeast the Qinghai-Tibet Plain using Lg waves, and research distributed characteristic of the Q code in this local, provides the science reference for this area's geophysics and the seismic active research.Summing up the analysis and study from above, we get following conclusions:1. Summarized shallow earthquakes wave characteristic which occurred in Qinghai-Tibet Plain recorded by Lanzhou digital seismic network. when an Qinghai-Tibet Plain earthquake from Lanzhou digital seismic network is 5°²0°scope, specially the magnitude about the Ms5.0, P and S wave is very weak in the seismographic, short period surface wave Lg1 and Lg2 are grow extremely, the shallow earthquake characteristic is obvious, well show influence that the ray traversing the upper mantle low velocity layer.2. We identified a range of the P and S wave shadow areas caused by mantle low-velocity layer in the Lanzhou digital seismic network. The shallow earthquake characteristic is most obvious while epicentral distance equal 7°¹6°for P wave, and epicentral distance equal 6°¹7°for S wave, moreover the upper mantle low velocity layer effect on S wave more obvious than P wave.3. Take Tibet earthquake as the example, We used simulation and filter processing methods, specially utilized seismic array processing technology recognition weak phase, improved the accuracy of the seismic phase recognition.4. We calculated the value of media properties Q code of the northeast Qinghai-Tibet Plain using the Lanzhou digital seismic network's data, studied the Q code distribution characteristic in the northeast Qinghai-Tibet Plain. The result showed that Lg wave's Q₀ value distribution with the geologic structure activity of the northeastern Qinghai-Tibet Plain is related, furthermore, related with this area's activity faults distribution.