New maps of crustal thickness and Vp/Vs in Alaska and western Canada were obtained using P receiver functions recorded at 198 stations from the USArray Transportable Array and the Alaska Regional Network. Our results indicate that topography and Moho depth are correlated as crustal thickness varies from 28 to 43 km across Alaska. A thick crust occurs under the mountains in the south and north with relatively thin crust in central Alaska. The deepest crustal root beneath the Brooks Range may have lost its buoyancy based on Airy isostasy. In addition, a buoyant upper mantle is required to support the high topography in east central Alaska. Vp/Vs is determined between 1.7 and 1.8 beneath most of Alaska except a high average of 1.9 in the south central region. We attribute this high Vp/Vs to the underplating of Yakutat and Pacific oceanic crust.
Gas hydrate is a new energy in the 21st century with the characteristics of high energy density, huge amount of resources and cleaning. It has important significances for resources development, environmental protection and global climate changing. Due to the limitations of the occurrence mode and the technical level of marine gas hydrates, at present, the development and utilization of the resources are still tentative. This article analyzed and evaluated several key technologies to develop marine gas hydrates, that is depressurization, thermal methods, chemical injection method, CO2 replacement method, and fluorine gas+microwave method.
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