HR: 0830h
AN: S21D-0324    [PDF]
TI: 3D Velocity and Hypocentre Distribution About a Cone-Volcano: Mt Taranaki, New Zealand
AU: * Sherburn, S
EM: sherburn@esc.cam.ac.uk
AF: Bullard Laboratories Cambridge University, Madingley Rd, Cambridge, CB3 0EZ United Kingdom
AU: * Sherburn, S
EM: sherburn@esc.cam.ac.uk
AF: Institute of Geological and Nuclear Sciences, Wairakei Research Centre Private Bag 2000, Taupo, 2370 New Zealand
AU: White, R
EM: rwhite@esc.cam.ac.uk
AF: Bullard Laboratories Cambridge University, Madingley Rd, Cambridge, CB3 0EZ United Kingdom
AB: Mt Taranaki is a 2518 m andesite cone-volcano (last eruption AD1755) within an oil-bearing sedimentary basin approximately 50 km west of the deepest part of the Benioff zone beneath the North Island of New Zealand. It is the most recent of a series of volcanoes that have erupted in the Taranaki region in the last 1.7 million years. Although a permanent six-station seismic network monitors Mt Taranaki for signs of unrest, little is known of the structure at the depths earthquakes occur and magma maybe stored. This information is vital for interpreting precursors to any future eruption. For nine months in 2001-2002, a temporary network of 75 three-component, broadband (0.03 - 50 Hz) seismographs (area c. 100 km by 100 km) was used to collect data to image crustal structure and accurately locate earthquakes in the Taranaki region. Three hundred and eighty-nine earthquakes were located using more than 15,000 phase picks (55% P and 45% S). A joint inversion for 1D Vp, Vs and hypocentres was undertaken using Velest followed by a 3D inversion for Vp, Vp/Vs ratio and hypocentres using Simul2000. The base of the seismogenic zone increases gradually from a depth of 20 km immediately west of Mt Taranaki to 35 km deep 100 km to the east, corresponding to a previously observed increase in crustal thickness. The area close to Mt Taranaki is anomalous in that there are few earthquakes and all are shallower than 10 km. Within the upper 5-10 km of the crust Vp is closely related to surface geology, being high beneath Mt Taranaki, low beneath the surrounding sedimentary basin, and very high to the east of the basin. We present the Vp and Vp/Vs structure and hypocentre distribution of the Taranaki region and discuss features that can be attributed to volcanism at Mt Taranaki and older volcanic centres.
DE: 7230 Seismicity and seismotectonics
DE: 7280 Volcano seismology (8419)
SC: Seismology [S]
MN: 2003 Fall Meeting