Banca de QUALIFICAÇÃO: THAYANE SAMARA DA CUNHA VICTOR

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : THAYANE SAMARA DA CUNHA VICTOR
DATA : 25/06/2018
HORA: 08:30
LOCAL: Laboratório Sismológico - (LabSis/UFRN)
TÍTULO:

Sedimentary architecture of the Parnaíba basin with high-frequency receiver functions

PALAVRAS-CHAVES:

Passive-source seismology, sedimentary architecture, receiver function.

PÁGINAS: 24
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

This work aims at assessing the performance of passive-source seismology in characterizing the stratigraphy of the intracratonic Parnaíba basin. To this end, receiver function (RF) estimates were developed at ten short-period and three broadband seismic stations located in the central portion of the basin. RFs were obtained through a deconvolution process that removes the signature of the source, instrument, and distant propagation from the recorded seismogram, leaving the contribution of local propagation under the recording station. Using hig-frequency RFs (Gaussian width of 5.0 and 10.0), two different approaches were utilized to estimate thickness of the sedimentary package and bulk Vp/Vs ratio for each site. The first approach consisted of a visual identification of P-to-S conversions making up the RFs and manual picking of the corresponding S-P travel-times; the final result for each station was given as an average of the estimates obtained from each individual RF. The second approach consisted of a joint analysis of all RFs for a given station, in which the amplitudes of the RFs were stacked along theoretical moveout curves for the Ps phases and multiples through a systematic search for thickness (H) and Vp/Vs ratio (κ). In this approach, also known as H-κ stacking, the final estimates for H and Vp/Vs ratio are provided by the maximum of the stacking surface. The estimates range from 1.8 to 3.1 km for sedimentary thickness, and from 1.6 to 2.5 for bulk Vp/Vs ratio. The results from both approaches and Gaussian widths were compared, concluding that a Gaussian width of 10.0 displays the best resolution and performance. Our sedimentary thickness estimates, however, were found inconsistent with those developed for the central portion of the Parnaíba basin from independent studies. According to analysis of seismic profiles, borehole data, and seismic noise autocorrelation functions, our thickness estimates are more consistent with depths to intra-sedimentary velocity contrasts, which are possibly related to Late Cretaceous diabase sills within the basin’s sedimentary sequence. Thus, the next step in this work will be to refine our results by developing 1-D Earth models through forward-modeling of the RF waveforms to, if at all possible, be used in a joint inversion with high-frequency dispersion curves.

MEMBROS DA BANCA:
Interno - 1451214 - ADERSON FARIAS DO NASCIMENTO
Interno - 1315614 - DAVID LOPES DE CASTRO
Presidente - 1863578 - JORDI JULIA CASAS