Design and Construction of System for Marine Geophysics Data Sharing Based on WebGIS

A browser/server system has been developed for the purpose of marine geophysical data sharing based on WebGIS technology, which uses MapServer open source system and ORACLE Data- base Management System. The main steps during development, including system design and imple- mentation, are discussed in this article. The system can provide convenient, efficient, and interactive marine geophysical information sharing and visualization services through Internet or Intranet to im- prove data exchange and utilization.

Progress in Antarctic marine geophysical research by the Chinese Polar Program

Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antarctic Peninsula between then and 1991/1992. After a 20 year hiatus, Antarctic marine geophysical research was relaunched by the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs （known simply as the Chinese Polar Program） in 2011/2012. Integrated geophysical surveys have been carried out annually since, in Prydz Bay and the Ross Sea. During the last 5 years, we have acquired about 5500 km of bathymetric, gravimetric, and magnetic lines; more than 1800 km of seismic reflection lines; and data from several heat flow and Ocean Bottom Seismometer （OBS） stations. This work has deepened understandings of geophysical features and their implications for geological tectonics and glacial history in Antarctica and its surrounding seas. Compiled Antarctic Bouguer and Airy isostatic gravity anomalies show different features of tectonics between the East Antarctic stability and West Antarctic activity. Calculated magnetic anomalies, heat flow anomalies and lithospheric anisotropy offshore of Prydz Bay may imply high heat capacity of mantle shielded by the continental shelf lithosphere, but high heat dissipation of mantle due to the Cretaceous breakup of Gondwana along the continent and ocean transition （COT）, where large sediment ridges would be brought about by the Oligocene ice sheet retreat and would enlarge free-air gravity anomalies. In the western Ross Sea, CHINARE seismic profiles indicate northern termination of the Terror Rift and deposition time of the grounding zone wedge in the northern JOIDES Basin.

Tectonics of the Indo-Australian Plate Near the Ninetyeast Ridge Constrained from Marine Gravity and Magnetic Data

Although the Indo-Australian plate near the Ninetyeast Ridge is important for understanding the formation of new plate boundaries, its tectonic problems are complex and most of them are poorly known. This paper made a detailed tectonic analysis based on the data of bathymetry, gravity and magnetics. Bathymetry and gravity maps show morphological features of many folds, which are related to the intraplate deformation of the Indo-Australian plate due to the collision between the Indian and Asian plates. Gravity anomalies show the structure of fracture zones, which are caused by the seafloor spreading and transform faulting. The characteristics of the folds and fracture zones are consistent with the hypothesis that diffuse plate boundaries and redefined plate components would occur within the Indo-Australian plate. In addition, compiled magnetic data demonstrate magnetic lineations, abandoned spreading centers, southward ridge jumps and plate motions. These features provide useful information for rebuilding the tectonic evolution history of the study area. Magnetic anomalies suggest that an additional plate boundary of transform fault type is developing.

Geophysical implications for the formation of the Tamu Massif–the Earth's largest single volcano–within the Shatsky Rise in the northwest Pacific Ocean

Recent geophysical research programs survey the Tamu Massif within the Shatsky Rise oceanic plateau in the northwest Pacific Ocean to understand the formation of this immense volcano and to test the forma- tion hypotheses of large igneous province volcanism. Massive sheet basalt flows are cored from the Tamu Massif, implying voluminous eruptions with high effusion rates. Seismic reflection data show that the Tamu Massif is the largest single volcano on Earth, characterized by a central volcanic shield with low- gradient flank slopes, implying lava flows emanating from its center and spreading massive area on the seafloor. Velocity model calculated from seismic refraction data shows that crustal thickness has a negative correlation with average velocity, implying a chemically anomalous origin of the Tamu Massif. Seismic refraction and reflection data reveal a complete crustal structure across the entire vol- cano, featured by a deep crust root with a maximum thickness of -30 kin, and Moho geometry is consis- tent with the Airy lsostasy. These recent findings provide evidence for the two end-member formation models： the mantle plume and the plate boundary, Both are supported by some results, but both are not fit with some either. Consequently, plume-ridge interaction could be a resolution that awaits future investigations.