HR: 0830h
AN: S31D-0790    [PDF]
TI: Using Array Seismology to Probe the Deep Earth With Core Seismic Phases
AU: * Black, J A
EM: jenny@liv.ac.uk
AF: University of Liverpool, Department of Earth Sciences, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AU: Thomas, C
EM: tine@liv.ac.uk
AF: University of Liverpool, Department of Earth Sciences, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AB: Much work is undertaken to investigate the structure of the deep Earth, i.e. the core and lower mantle. Researching these regions is important, as they are thought to govern the generation of the Earth's magnetic field, as well as mantle convection. The deep mantle region includes the core-mantle interaction zone, and is potentially the origin of plumes, and the graveyard for slabs. Much controversy exists regarding the nature of the inner core, in particular its anisotropy and rotation. Up to now, seismological studies of the Earth's core have focused primarily on travel time deviations. These locate anomalous regions, but cannot determine the nature of the anomaly. The rays may have been deviated along an anomalous path (backazimuth deviation), or travelled at an anomalous phase velocity (slowness deviation). The work presented here utilises array seismology to further examine anomalies previously located by studying travel time deviations. The slowness and backazimuth of core seismic phases are calculated, and compared with global velocity models. Deviations of the different phases are analysed to resolve the location of the anomalous regions. The results are then compared with travel time deviations. This method will be employed globally, utilising arrays that lie at a suitable epicentral distance from relatively deep, strong events. Currently two arrays have been used, the German Regional Seismic Network (GRSN) and the Alaska Seismic Network (ASN). Earthquakes in Tonga-Fiji are received by the GRSN, and data from the ASN is used to further investigate the anomalous South Sandwich Islands to Alaska path. This path has been shown in recent studies to have strong anisotropy and is also used to study rotations of the inner core. Results show that deviations are present in all three phases (PKPab, PKPbc and PKPdf); deviations vary for the different paths. The Tonga-Fiji to Germany path has particularly deviated backazimuth values for all three phases, possibly indicative of lower mantle structure. The South Sandwich Island to Alaska path shows deviations particularly in the PKPdf branch (the branch that travels through the inner core).
DE: 7200 SEISMOLOGY
DE: 7207 Core and mantle
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Seismology [S]
MN: 2003 Fall Meeting