Seismic exploration-scale velocities and structure from ambient seismic noise (>1 Hz)

<p>Zagros continental collision zone (S-SW Iran) is tectonically active and extends over 1800 km contained most part of hydrocarbon reservoirs worldwide. The DehDasht region is located in the southeast of the Dezful embayment in the Zagros fold-and-thrust belt. The existence of an evaporation layer with high velocity features is the main challenge to apply classical seismic exploration in this region. However, ambient seismic noise carries valuable information about the propagation path; hence it could be a useful tool for studying crustal structure in the DehDasht region. For this purpose, we used up to 9 months of continuous data recorded by 107 stations in the area with ~16 &#215; ~24 km<sup>2</sup>. All stations are equipped with broadband (120s) sensors recording at 100 sps. The standard ambient seismic noise processing was done as outlined by Bensen et al. (2007), and optimize empirical Green&#8217;s function (EGF) was retrieved based on the WRMS stacking method. Afterward, Rayleigh wave dispersion measurements were calculated using the FTAN approach in the period range of 0.1-5.0 s, then the inversion procedure was performed by the Fast-Marching Method with an inversion cell size of 2&#215;2 km. Our group velocity tomographic maps show a high velocity anomaly in the Khaviz Mountain belt (west part of the study area) is generally linked to the older, consolidated bodies while two low velocity anomalies are related to the presence of fluids and or younger structures.</p>

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Delineation of sedimentary basin structure beneath the Banyumas Basin, Central Java, Indonesia, using ambient seismic noise tomography

Geoscience Letters ◽

10.1186/s40562-021-00202-x ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Ahmad Setiawan ◽

Zulfakriza Zulfakriza ◽

Andri Dian Nugraha ◽

Shindy Rosalia ◽

Awali Priyono ◽

...

Keyword(s):

Seismic Noise ◽

Sedimentary Basin ◽

Sedimentary Rocks ◽

Vertical Component ◽

Seismic Exploration ◽

Ambient Seismic Noise ◽

Central Java ◽

Sediment Deposits ◽

Cross Correlations ◽

Grid Points

AbstractSubsurface images of an area with a thick volcanic layer generally cannot be well-imaged with conventional seismic exploration (seismic reflection) due to seismic wave scattering. Another method is needed to obtain an accurate subsurface image in a thick volcanic layer area. In this study, we applied ambient noise tomography (ANT) to image the shear-wave velocity (Vs) structure in the Banyumas Basin, Central Java, Indonesia, which has relatively thick volcanic layers. We aimed to delineate the sediment deposits and the sedimentary thickness in this area through the utilization of ambient seismic noise. The application of cross-correlations from ambient seismic noise has been widely applied in numerous locations to obtain a greater understanding of subsurface structures. In this study, more than 1000 pairs of vertical component cross-correlations were used to estimate the Green's Function of the Rayleigh wave. The Neighbourhood Algorithm (NA) was utilized to invert the dispersion curves at 121 grid points which were used to obtain a vertical depth profile of 1D Vs. The Vs map results show that the low Vs tend to trend in a northwest–southeast direction associated with two areas: the Majenang low, and the Citanduy low. The presence of low Vs values corresponds with Middle Miocene–Pliocene sedimentary rocks. Meanwhile, the high Vs values in this area might correspond with Oligocene–Early Miocene volcanic products and Eocene sediment. Our study was also able to reveal the thickness of sedimentary rocks in the Banyumas sedimentary basin, which is believed to have hydrocarbon potential.

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Reflection images from ambient seismic noise

Geophysics ◽

10.1190/1.3193529 ◽

2009 ◽

Vol 74 (5) ◽

pp. A63-A67 ◽

Cited By ~ 142

Author(s):

Deyan Draganov ◽

Xander Campman ◽

Jan Thorbecke ◽

Arie Verdel ◽

Kees Wapenaar

Keyword(s):

Surface Wave ◽

Green’S Function ◽

Green's Function ◽

Seismic Noise ◽

Seismic Exploration ◽

Ambient Seismic Noise ◽

Reflection Data ◽

Parallel Lines ◽

Reflection Image ◽

Sirte Basin

One application of seismic interferometry is to retrieve the impulse response (Green’s function) from crosscorrelation of ambient seismic noise. Various researchers show results for retrieving the surface-wave part of the Green’s function. However, reflection retrieval has proven more challenging. We crosscorrelate ambient seismic noise, recorded along eight parallel lines in the Sirte basin east of Ajdabeya, Libya, to obtain shot gathers that contain reflections. We take advantage of geophone groups to suppress part of the undesired surface-wave noise and apply frequency-wavenumber filtering before crosscorrelation to suppress surface waves further. After comparing the retrieved results with data from an active seismic exploration survey along the same lines, we use the retrieved reflection data to obtain a migrated reflection image of the subsurface.

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