Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano

Details Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano

Feb 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003geoji.152..486a&link_type=abstract

Geophysical Journal International, Volume 152, Issue 2, pp. 486-496.

Astronomy and Astrophysics

Astronomy

5

Crustal Structure, Explosion Seismology, Low-Velocity Layer, S Waves, Seismic Tomography, Volcanic Structure

Scientific paper

In this paper, we show how the migration of active seismic data can be used to identify and position a seismic discontinuity in a complex medium, and how the amplitude variations of the converted P to S waves can be interpreted to constrain the seismic velocities below the interface. For the application we turn our attention on Mt Vesuvius, an active volcano threatening a densely populated area. To better define its plumbing system, we investigate a mid-crust seismic discontinuity first identified by Zollo et al. (1996, Science,274, 592-594) and assumed to be the top of a layer containing low-velocity material. We deduce a reference velocity model from previous works on first arrival times, and use it to migrate PP reflected and PS converted waves. In the migration image, the interface extends at least 20000 m NE and 20000 m SW of the volcano, at the depth of 8000 m, and with a mean dip less than 3 per cent. The migration of finite-difference synthetics exclude the fact that the migrated phases interpreted as 8000 m deep reflections or conversions might be multiples in the shallow layers.
The PS and first arrival amplitudes are compared at a fixed station and for all the shots to determine the variations of the P-to-S conversion coefficient with the angle of incidence. It appears to vary very slowly over the whole range of incidence angle at disposal (50∘-80∘). This implies a dramatic drop of S-wave velocity from approximately 3600 m s-1 above to less than 1000 m s-1 below the interface. The smoothness of the variations indicate that the P-wave velocity also diminishes across the interface.
The very low S-wave velocity, other geophysical observations at Vesuvius and in other volcanic systems, lead to the conclusion that below the 8000 m discontinuity there is a very extended layer of hot, partially molten material.

Affiliated with

Also associated with

No associations

Rating

Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-922164