Seismogram Analysis of the Earthquakes in Sumatra on WRAB Observation Station: S Wave Velocity Structure on Subduction Zone of Sumatra-Java.
AbstractThe S wave velocity structure at subduction zone under Sumatra-Java was investigated through seismogram analysis in time domain and three Cartesianâ€™s components simultaneously. The main data set was the comparison between the measured seismogram and the synthetic one, not the travel time data. The synthetic seismogram was calculated with the GEMINI method. The seismogram comparison shows that the global earth mantle of PREMAN gives deviating synthetic seismogram and has later arrival times than the measured one. The gradient Ã¢h in the upper mantle is altered to positive from its negative slope as in the PREMAN model, and positive corrections are added to the zero order of polynomialâ€™s coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, were obtained on the surface waves of Love and Rayleigh, the S and SS mantle and repetitive depth waves. The additional positive corrections were also confirmed by a well fitting on the repetitive depth waves. This result expresses that part of the earth mantle that due to tectonic processes has positive anomaly on S wave velocity and vertical anisotropy in all of the earth mantle layers.
Vasco, D., Johnson, L., Pulliam, R., Lateral variations in mantle velocity structure and discontinuities determined from P, PP, S, SS, and SS-ScS travel time residuals, J. Geophys. Res., 100, 24037.24059, 1995.
Zhou, H., A high-resolution P wave model for the top 1200 km of the mantle, J. Geophys. Res., 101, 27791.27810, 1996.
Grand, S., van der Hilst, R., Widiyantoro, S., Global seismic tomography: a snapshot of convection in the Earth, GSA Today, 7, 1.7, 1997.
van der Hilst, R., Widiyantoro, S., Engdahl, E., Evidence for deep mantle circulation from global tomography, Nature, 386, 578.584, 1997.
Bijwaard, H., Spakman, W., Engdahl, E., Closing the gap between regional and global travel time tomography, J. Geophys. Res., 103, 30055.30078, 1998.
Boschi, L., Dziewonski, A., High- and low-resolution images of the Earthfs mantle: Implications of different approaches to tomographic modeling, J. Geophys. Res., 104, 25567.25594, 1999.
Zhao, D., Seismic structure and origin of hotspots and mantle plumes. Earth Planet, Sci. Lett., 192, 251.265, 2001.
Zhao, D., Global tomographic images of mantle plumes and subducting slabs: insight into deep Earth dynamics, Physics of the Earth and Planetary Interiors, 146, 3.34, 2004.
Lay, T., Williams, Q., Garnero, E., The core.mantle boundary layer and deep Earth dynamics, Nature, 392, 461.468, 1998.
Garnero, E., Heterogeneity of the lowermost mantle, Annu. Rev. Earth Planet. Sci., 28, 509.537, 2000.
Nataf, H., Seismic imaging of mantle plumes, Annu. Rev. Earth Planet. Sci., 28, 391.417, 2000.
Dziewonski, A., Mapping the lower mantle: determination of lateral heterogeneity in P velocity up to degree and order 6, J. Geophys. Res., 89, 5929.5952, 1984.
Su, W., Woodward, R., Dziewonski, A., Degree 12 model of shear velocity heterogeneity in the mantle, J. Geophys. Res., 99, 6945.6980, 1994.
Mooney, W., Laske, G., Master, G., CRUST 5.1: a global crustal model at 5. ~ 5., J. Geophys. Res., 103, 727.747, 1998.
Flanagan, M., Shearer, P., Global mapping of topography on transition zone velocity discontinuities by stacking SS precursors, J. Geophys. Res., 103, 2673.2692, 1998.
Engdahl, E., van der Hilst, R., Buland, R., Global teleseismic earthquake relocation with improved travel times and procedures for depth determination, Bull. Seismol. Soc. Am., 88, 722.743, 1998.
Bulland, R. & Chapman, C., Travel time Calculation, BSSA, 73, 1271-1302, 1983.
Dalkolmo, J., Synthetische Seismogramme fuer eine sphaerisch symmetrische, nichtrotierend Erde durch direkte Berechnung der Greenschen Funktion, Diplomarbeit, Inst. fuer Geophys., Uni. Stuttgart, 1993.
Friederich, W. & Dalkolmo, J., Complete synthetic seismograms for a spherically symmetric earth by a numerical computation of the green's function in the frequency domain, Geophys. J. Int., 122, 537-550, 1995.
Dziewonski, A.M. & Anderson, D.L., Preliminary reference Earth model, Phys. of the Earth and Plan. Int., 25, 297 - 356, 1981.
Wysession, M., Lay, T., Revenaugh, J., The D" discontinuity and its implications, In: Gurnis, M., Buffett, B., Knittle, K., Wysession, M. (Eds.), The Core-Mantle Boundary. AGU, pp. 273-297, 1998.
L. Boschi, A.M. Dziewonski, Whole Earth tomography from delay times of P, PcP, and PKP phases: lateral heterogeneities in the outer core or radial anisotropy in the mantle?, J. Geophys. Res., 105, 13675-13696, 2000.