Seismic coda wave is the tail portion of the earthquake record after main arrivals. Studies on the coda usually focus on high-frequency data within several hours after regional events and attribute them to the scattering effect of the heterogeneities inside the earth. Here, we use records of seven large earthquakes at globally distributed seismic stations to examine the decay of long-period (100 s to 300 s) coda in the time window of 10,000 s to 140,000 s after the origin time and fit it with a statistical model. The geometric spreading effect in the estimated initial energy and a location-independent equivalent attenuation coefficient indicate that the long-period coda energy is less affected by the heterogeneity-induced scattering effect than that of shorter-period coda. The coda energy can reach the earth's inner core and can be explained by a 1D earth model, making it more effective for constraining the global attenuation model. It also has the potential to determine the magnitudes of large earthquakes and to explore the interior of planetary bodies. 相似文献
The paper discusses quantitatively the influence of the Yutian MS7.4 earthquake of March 21, 2008 and Wuqia MS6.9 earthquake of October 5, 2008 on regional seismicity in Xinjiang, and explains primarily the possible reason of earthquake activity feature in Xinjiang after the Yutian MS7.4 earthquake by analyzing the static Coulomb failure stress change produced by the Yutian MS7.4 earthquake and Wuqia MS6.9 earthquake, and the seismicity feature of MS?≥3 earthquakes in the positive Coulomb stress change region of Kashi-Wuqia joint region, the central segment of Tianshan Mountain and Kalpin block. The result shows that the Yutian MS7.4 earthquake of March 21, 2008, may encourage the Wuqia MS6.9 earthquake of October 5, 2008, and the Yutian MS7.4 earthquake and Wuqia MS6.9 earthquake may change the seismicity state in the central segment of Tianshan Mountain, Kalpin block and Kashi-Wuqia joint region, and encourage the subsequent MS?≥3 earthquakes.