During the process of preparation and occurrence of a large earthquake, the stress-strain state along the fault zone has close relation with the weak seismicity around the fault zone. The seismic energy release near t...During the process of preparation and occurrence of a large earthquake, the stress-strain state along the fault zone has close relation with the weak seismicity around the fault zone. The seismic energy release near the fault zone before an earthquake can better reflect the dynamic process of earthquake preparation. Thus, in this paper, the method of natural orthogonal function expansion has been adopted to discuss the time variation about the energy field of the seismic activity along the Longmenshan fault zone before the Wenchuan MsS. 0 earthquake, 2008. The results show that evident short-term rise changes appeared in the time factors of the typical field corresponding to several key eigenvalues of the energy field along the Longmenshan fault zone before the Wenchuan earthquake, probably being the short-term anomaly message for this earthquake. Through contrastive analysis of earthquake examples such as the 1976 Tangshan earthquake, the authors think that the study of time variation of energy field of seismicity along active fault zone will be helpful for conducting intentional and intensive earthquake monitoring and forecast in active fault regions with high seismic risk based on medium- and long-term earthquake trend judgment.展开更多
The construction of the Qinghai-Xizang Railway is facing some challenges posed by the presence of warm and ice-rich permafrost and predicted climate warming. To resolve these issues and ensure the railway a success, a...The construction of the Qinghai-Xizang Railway is facing some challenges posed by the presence of warm and ice-rich permafrost and predicted climate warming. To resolve these issues and ensure the railway a success, adjustments will have to be made in design strategies and principles. This paper presents several examples of permafrost-distribution anomaly caused by site-specific conditions. It analyzes the mechanism through which these local factors influence the occurrence and preservation of permafrost by modifying the heat convection and conduction patterns, and the amount of solar radiation received by the ground surface. A good understanding of these anomalies in permafrost occurrence is significant as it may provide some hints on the techniques and measures we can use to artificially simulate similar effects. A number of measures can be taken to lower ground temperature and to counter the effect of cli-mate warming. These measures include use of proper roadbed material and configuration, in order to adjust solar radiation, heat convection and conduction patterns. It is recommended that a new proactive approach be adopted in the railway design. This approach emphasizes the use of all the above-mentioned measures to cool down the roadbed. This is different from previous methods of preventing permafrost from thawing by utilizing more thermal resistant materials.展开更多
文摘During the process of preparation and occurrence of a large earthquake, the stress-strain state along the fault zone has close relation with the weak seismicity around the fault zone. The seismic energy release near the fault zone before an earthquake can better reflect the dynamic process of earthquake preparation. Thus, in this paper, the method of natural orthogonal function expansion has been adopted to discuss the time variation about the energy field of the seismic activity along the Longmenshan fault zone before the Wenchuan MsS. 0 earthquake, 2008. The results show that evident short-term rise changes appeared in the time factors of the typical field corresponding to several key eigenvalues of the energy field along the Longmenshan fault zone before the Wenchuan earthquake, probably being the short-term anomaly message for this earthquake. Through contrastive analysis of earthquake examples such as the 1976 Tangshan earthquake, the authors think that the study of time variation of energy field of seismicity along active fault zone will be helpful for conducting intentional and intensive earthquake monitoring and forecast in active fault regions with high seismic risk based on medium- and long-term earthquake trend judgment.
文摘The construction of the Qinghai-Xizang Railway is facing some challenges posed by the presence of warm and ice-rich permafrost and predicted climate warming. To resolve these issues and ensure the railway a success, adjustments will have to be made in design strategies and principles. This paper presents several examples of permafrost-distribution anomaly caused by site-specific conditions. It analyzes the mechanism through which these local factors influence the occurrence and preservation of permafrost by modifying the heat convection and conduction patterns, and the amount of solar radiation received by the ground surface. A good understanding of these anomalies in permafrost occurrence is significant as it may provide some hints on the techniques and measures we can use to artificially simulate similar effects. A number of measures can be taken to lower ground temperature and to counter the effect of cli-mate warming. These measures include use of proper roadbed material and configuration, in order to adjust solar radiation, heat convection and conduction patterns. It is recommended that a new proactive approach be adopted in the railway design. This approach emphasizes the use of all the above-mentioned measures to cool down the roadbed. This is different from previous methods of preventing permafrost from thawing by utilizing more thermal resistant materials.
