- Open Access
Broadband converted phases from midmantle discontinuities
Earth, Planets and Space volume 50, pages987–997(1998)
A technique for detecting intermediate-period (6–12 s) Sd P phases converted from S to P at a depth d in the source region is described. Previously, these phases were detected in short-period array recordings of deep events. The main idea of our technique is to deconvolve the vertical component of a single record by the S waveform, and to stack the deconvolved components of a number of records, with appropriate time-shift corrections accounting for the difference of epicentral distance. Using this technique, the phases converted from discontinuities at around 660 km, 860 km, 1070 km, and ‘1170’ km depths beneath Sunda arc are detected at seismograph stations in central and eastern Asia. Our data on ‘1070 km’ discontinuity are very consistent with those inferred from short-period recordings of the same events at the J-array in Japan (Niu and Kawakatsu, 1997), but favour a few different discontinuities in the midmantle, rather than one with a strongly variable depth. When compared with a tomographic model of the mantle for the same region, our data suggest that ‘1070 km’ discontinuity may act as a barrier for the downgoing lithospheric slabs.
Aki, K. and P. Richards, Quantitative Seismology: Theory and Methods, 932 pp., W. H. Freeman and Co., 1980.
Barley, B. J., J. A. Hudson, and A. Douglas, S to P scattering at the 650 km discontinuity, Geophys. J. R. astr. Soc., 49, 773–777, 1982.
Bock, G. and J. Ha, Short-period S-P conversion in the mantle at a depth near 700 km, Geophys. J. R. astr. Soc., 77, 593–615, 1984.
Estabrook, Ch., G. Bock, and R. Kind, Investigation of mantle discontinuities from a single deep earthquake, Geophys. Res. Lett., 21, 1495–1498, 1994.
Farra, V., L. P. Vinnik, B. Romanowicz, G. L. Kosarev, and R. Kind, Inversion of teleseismic S particle motion for azimuthal anisotropy in the mantle: A feasibility study, Geophys. J. Int., 106, 421–431, 1991.
Fuchs, K. and G. Mueller, Computation of synthetic seismograms with the reflectivity method and comparison with observations, Geophys. J. R. astr. Soc., 23, 417–433, 1971.
Goes, S., L. Ruff, and N. Winslow, The complex rupture process of the 1996 deep Flores, Indonesia earthquake (Mw 7.9) from teleseismic P-waves, Geophys. Res. Lett., 24, 1295–1298, 1997.
Kawakatsu, H. and F. Niu, Seismic evidence for a 920-km discontinuity, Nature, 371, 301–305, 1994.
Kennett, B. L. N. and E. R. Engdahl, Travel times for global earthquake location and phase identification, Geophys. J. Int., 105, 429–465, 1991.
Kind, R. and G. Mueller, Computations of SV waves in realistic Earth models, J. Geophys., 41, 142–162, 1975.
Niu, F. and H. Kawakatsu, Direct evidence of the undulation of the 660-km discontinuity beneath Tonga: comparison of Japan and US regional array data, Geophys. Res. Lett., 22, 531–534, 1995.
Niu, F. and H. Kawakatsu, Depth variation of the midmantle seismic dis-continuity, Geophys. Res. Lett., 24, 429–432, 1997.
Richards, M. A. and C. W. Wicks, Jr., S-P conversion from the transition zone beneath Tonga and the nature of the 670 km discontinuity, Geophys. J. Int., 101, 1–35, 1990.
Sakurai, T., M. Obayashi, and Y. Fukao, Tomographic image of slab and mantle plume, Program and Abstracts, Seism. Soc. Japan, 1, 624, 1995 (in Japanese).
Vidale, J. E. and H. M. Benz, Upper-mantle seismic discontinuities and the thermal structure of subduction zones, Nature, 356, 678–682, 1992.
Vinnik, L. P., Detection of waves converted from P to SV in the mantle, Phys. Earth Planet. Inter., 15, 39–45, 1977.
Vinnik, L., G. Kosarev, and N. Petersen, Mantle transition zone beneath Eurasia, Geophys. Res. Lett., 23, 1485–1488, 1996.
Wicks, C. W. and M. A. Richards, A detailed map of the 660-kilometer dis-continuity beneath the Izu-Bonin subduction zone, Science, 261, 1424–1427, 1993.
Wood, B. J., The effect of H2 O on the 410-km seismic discontinuity, Science, 268, 74–76, 1995.
About this article
Cite this article
Vinnik, L., Niu, F. & Kawakatsu, H. Broadband converted phases from midmantle discontinuities. Earth Planet Sp 50, 987–997 (1998). https://doi.org/10.1186/BF03352193
- Subduction Zone
- Focal Mechanism
- Epicentral Distance
- Synthetic Seismogram
- Fresnel Zone