In this study, we collected 1156 broadband vertical components records at 22 digital seismic stations in Xinjiang region, Urumqi station, and 7 stations in the adjacent regions during the period of 1999-2003. The reco...In this study, we collected 1156 broadband vertical components records at 22 digital seismic stations in Xinjiang region, Urumqi station, and 7 stations in the adjacent regions during the period of 1999-2003. The records were firstly processed by the stacked spectral ratio method to obtain Q0 (Q at 1 Hz) and the frequency correlation factor η corresponding to each path. Based on the results, the distribution images of Q0 and η in 1°×1° grids for Xinjiang region were gained by the back-projection technique. The results indicate that Q0 is high (300-450) in the Tarim platform and marginal Siberian platform, while Q0 is low (150-250) in the southern regions as west Kunlun fold system and Songpan-Ganzi fold system. In the northern regions as Junggar fold system and Tianshan fold system, Q0 is also low (250-300) and η varies between 0.5 and 0.9.展开更多
We have collected 432 vertical component records from 45 stations of new CENC （China Earthquake Network Center） in Chinese mainland and adjacent regions. These records were used to calculate Q0 （Q at 1Hz） and η v...We have collected 432 vertical component records from 45 stations of new CENC （China Earthquake Network Center） in Chinese mainland and adjacent regions. These records were used to calculate Q0 （Q at 1Hz） and η values of Lg coda from each station by the stack spectral ratio （SSR） method. Then the tomography method was applied to obtaining lateral variation of Q0 and η values in Chinese mainland and adjacent regions. The result indicates that Q0 value varies between 150 and 600 in the studied areas. Yunnan, southwest Sichuan, and northwest Myanmar show the lowest Q0 value （Q0〈240） and the crust of these regions is characterized by complicated crack and strong hydrothermal activity. The highest Q0 value （Qo〉510） exists in the border of southern Mongolia, Alxa and Ordos block. The η value varies between 0.45 and 0.75 in Chinese mainland and its adjacent regions.展开更多
Lg-waves propagate over long distances in the northern part of Africa and are recorded on the seismic station located close to Abeche (Chad). We have applied the well-known coda analysis method developed by Aki and Ch...Lg-waves propagate over long distances in the northern part of Africa and are recorded on the seismic station located close to Abeche (Chad). We have applied the well-known coda analysis method developed by Aki and Chouet [1] to study the Lg-wave anelastic attenuation in this area. We found a frequency dependence: Q( f ) = (650±34) f <sup>(0.77±0.2)</sup>. This result shows an average value of Q0 (Q0 ≈ 650) for earthquakes occurred in tectonic areas as the East African Rift system, Turkey, Greece and Red Sea. The higher value of Q0 (Q0 ≈ 800) is obtained for the event occurred in the middle of the stable plate close to the Tamanrasset (TAM) station in Algeria.展开更多
基金National Natural Science Foundation of China (49974012) and Joint Seismological Science Foundation of China (604004).
文摘In this study, we collected 1156 broadband vertical components records at 22 digital seismic stations in Xinjiang region, Urumqi station, and 7 stations in the adjacent regions during the period of 1999-2003. The records were firstly processed by the stacked spectral ratio method to obtain Q0 (Q at 1 Hz) and the frequency correlation factor η corresponding to each path. Based on the results, the distribution images of Q0 and η in 1°×1° grids for Xinjiang region were gained by the back-projection technique. The results indicate that Q0 is high (300-450) in the Tarim platform and marginal Siberian platform, while Q0 is low (150-250) in the southern regions as west Kunlun fold system and Songpan-Ganzi fold system. In the northern regions as Junggar fold system and Tianshan fold system, Q0 is also low (250-300) and η varies between 0.5 and 0.9.
基金The Crust and Upper Mantle Digital Structure Project of China and Joint Seismological Science Foundation of China (104060)
文摘We have collected 432 vertical component records from 45 stations of new CENC （China Earthquake Network Center） in Chinese mainland and adjacent regions. These records were used to calculate Q0 （Q at 1Hz） and η values of Lg coda from each station by the stack spectral ratio （SSR） method. Then the tomography method was applied to obtaining lateral variation of Q0 and η values in Chinese mainland and adjacent regions. The result indicates that Q0 value varies between 150 and 600 in the studied areas. Yunnan, southwest Sichuan, and northwest Myanmar show the lowest Q0 value （Q0〈240） and the crust of these regions is characterized by complicated crack and strong hydrothermal activity. The highest Q0 value （Qo〉510） exists in the border of southern Mongolia, Alxa and Ordos block. The η value varies between 0.45 and 0.75 in Chinese mainland and its adjacent regions.
文摘Lg-waves propagate over long distances in the northern part of Africa and are recorded on the seismic station located close to Abeche (Chad). We have applied the well-known coda analysis method developed by Aki and Chouet [1] to study the Lg-wave anelastic attenuation in this area. We found a frequency dependence: Q( f ) = (650±34) f <sup>(0.77±0.2)</sup>. This result shows an average value of Q0 (Q0 ≈ 650) for earthquakes occurred in tectonic areas as the East African Rift system, Turkey, Greece and Red Sea. The higher value of Q0 (Q0 ≈ 800) is obtained for the event occurred in the middle of the stable plate close to the Tamanrasset (TAM) station in Algeria.
