Double seismic zone in Tonga,
Kawakatsu, H.
Nature, 316,
53-55, 1985.
Abstract
Since the discovery of clear evidence for the presence of
a double seismic zone
beneath Japan$"" sup 1,2$,
seismologists have been searching for other double seismic zones.
Because double seismic zones have been found in
few other areas$"" sup 3,4,5,6$,
it has been believed that their presence is rare and depends strongly on
a peculiar combination of external
conditions (e.g., age of the descending slab, convergence rate)$"" sup 7$.
A new double seismic zone is found beneath the Tonga arc$"" sup 8$,
where it has been believed that the stress state
in the subducting slab is strongly down-dip compressional$"" sup 7,9,10$.
This new discovery of a Tonga double seismic zone suggests that
the double seismic zone is a more general feature of
subducting slabs and may be found in many other subduction zones.