Deep Earthquakes From the Pre-Digital ERA

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WPC 2 ' B Z R # X #| x HP LaserJet IIIP HPLSIIIP.PRS x @ , \ , | @Courier 10cpi Courier 10cpi (Bold) ? x x x , x 6 X @ 8 ; X @ ? x x x , d x ` B ; X | H H 8 2 Y 9218907 X ` h p x (# % '0* , .81 3 5@8 : H? A H 8 Okal H 8 H H @H H ' This research is to study the seismic structure of the Ontong Java Plateau, the largest expression of igneous activity of the ocean floor. Four seismic stations composed of PASSCAL instruments will be deployed for two years on the Micronesian islands of Chuuk, Pohnpei, Kosrae and Nauru. Earthquake sources in the Solomon subduction zone will be used to investigate the dispersion of surface waves over the plateau to measure seismic structure to depths on the order of 200 km. Concurrently, a number of body wave experiments will be conducted targeting the structural anisotropy of the crust and upper mantle in the area. The work is expected to provide answers to such questions as the exact thickness of the crust, the nature of the deep crust, the structure of the mantle (lid and underlying low velocity zone) of the plateau, and the extent and direction of anisotropy in the upper mantle. In turn, these parameters will put constraints on the environment and mechani sm of emplacement of the plateau in the Cretaceous. ***