Lianxing Wen -> Research -> Seismology -> Core-mantle boundary -> Comoros Hotspot
A deep "root" for a surface volcano?
Raypaths of PKPdf (PKIKP) and its precursors at a distance of 135 degree.
PKPdf is the P wave propagating through the inner core.
Seismic P wave could be deflected by the seismic scatterers
in the lower mantle beneath the source or/and the receiver.
The shaded regions indicate the scatterers
in the great-circle path,
which will produce seismic arrivals before the PKPdf phase.
The reference model is PREM and
the source depth is 500 km.
a) Technique using arrival times of
PKP precursors to locate seismic scatterers in the lower
mantle. The energy envelop of an observed vertical seismogram
is shown in the middle of the figure.
The great-circle path of this example PKP phase is also
shown in the figure.
The perspective scatterers producing the precursor onset energy are
located in two "isotime scatterer arcs" (blue arcs)
in the mantle beneath the source and the receiver.
The precursor energy and the
geographic locations of its associated perspective scatterers are
connected by lines.
The core-mantle boundary scattering is assumed in this example.
Stars and triangles represent events and stations used in
this study. Two boxes indicate two sampling regions,
with detailed results shown in Figs. 3b-3i;
b-e) probability of existence of seismic scatterers
in the lowermost mantle; and, f-i) number of seismograms sampling th
e
region.
Two depths of seismic scattering are assumed: the
core-mantle boundary (d-e,h-i) and 200 km above the
core-mantle boundary (b-c,f-g).
Open-circles are locations of hotspots.
Note that the "isotime scatterer arcs" overlay at the location
near (d) or just beneath (b) the Comoros hotspot.