Scattered P'P' waves observed at short distances

Bulletin of the Seismological Society of America
By: , and 

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Abstract

We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (ρt, ρr) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P′•d•P′, which can scatter from any depth, d, in the mantle.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Scattered P'P' waves observed at short distances
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120110157
Volume 101
Issue 6
Year Published 2011
Language English
Publisher Seismological Society of America
Contributing office(s) Rocky Mountain Mapping Center
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Bulletin of the Seismological Society of America
First page 2843
Last page 2854