Detailed Oceanic Crustal Modeling.

• Main Author: Helmberger,D V
• Other Authors: CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB
• Format: Text
• Language: English
• Published: 1984
• Subjects: Physical and Dynamic Oceanography; Numerical Mathematics; Acoustics; *OCEAN WAVES; *OCEAN MODELS; *OCEANIC CRUST; SHEAR PROPERTIES; SIMULATION; COASTAL REGIONS; MATHEMATICAL ANALYSIS; SEISMIC WAVES; ACOUSTIC ATTENUATION; EARTHQUAKES; ACOUSTIC VELOCITY; NORTH ATLANTIC OCEAN; STRUCTURAL GEOLOGY; PRIMARY WAVES(SEISMIC WAVES); EARTH MANTLE; Kirchoff Helmholtz integral equation; PE083399; North Atlantic; Northwest Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA148589; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA148589

The research performed under this contract can be divided into 3 main topics: changes in existing methods, Cagniard de-Hoop and WKBJ, which enable construction of synthetics for mixed path simulations; use of long period SH waves with source in the Northwest Atlantic and receivers on the northeast coast of North America to derive an oceanic upper mantle shear velocity model; and a technique based on evaluating the Kirchoff-Helmholtz integral for predicting the effect of near source or near receiver structure complexity on far field p waves. In Section II we assess the fact that recent models of upper mantle structure based on long period body waves (WWSSN) suggest large horizontal gradients, especially in shear velocities. Some changes in existing methods are required to construct synthetics for mixed path situations. This is accomplished by allowing locally dipping structure and making some modifications to generalized ray theory. In Section III, we have modeled the SH motion from earthquakes in the northwest Atlantic ocean to derive an oceanic upper mantle shear velocity model. In Section IV, we extend the Kirchoff-Helmholtz integral method to calculate acoustic potentials which transmit through three dimensional warped boundaries.