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Interstation correlograms of ambient seismic noise estimates used to estimate point source Green's functions between station BNA23 on the northwestern edge of the network and other stations. Waveforms were filtered between 0.125 and 1.0 Hz. The time length of cross-correlation extends from 0 to 100 s. Red line depicts group velocity of ∼2.3 km s -1 , and used as reference time to window dispersive train segment.
Source publication
S U M M A R Y We investigated the seismic shear wave velocity structure of the upper crust beneath the Ban-dung area in West Java, Indonesia, using ambient seismic noise tomography. We installed 60 seismographs to record ambient seismic noise continuously in the city of Bandung and its surrounding area for 8 months. After interstation cross-correla...
Contexts in source publication
Context 1
... order to facilitate estimation of the fundamental-mode Rayleigh wave group velocity, we conducted manual picking and windowing of the Rayleigh wave using bandpassed-filtered crosscorrelated signals. Fig. 2 shows an example of such correlograms filtered between 0.125 and 1 Hz (or period range 1-8 s), arranged with station BNA23 as a reference to other stations. The crosscorrelogram was measured by cross-correlating the time series data from a station located to the north relative to most of the other stations, and showing a prominent ...
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... with our previous result using different data set from Central Java (Yudistira & Widiyantoro 2016). In order to extract dispersive curves, windowing of the cross-correlated signals was conducted using a width of 16 s, that is 8 s before and after the picked time. The picked time is a time estimated as the arrival time of dispersive wave, in Fig. 2 chosen near the intersection between the red line and time axis of each cross-correlation. The minimum distance between stations whose cross correlations give clear dispersive wavetrains is 5 km and the maximum distance is 60 km (BNA23-BNA36). We refer to the windowed cross correlation as the emperical Green's functions ...
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... of 1.15 km s -1 , a damping value of 200 and a smoothing parameter of 200 (see eq. 2 of Saygin & Kennett 2010). In general, the checkerboard pattern is recovered where the ray path coverage is good, particularly in the Bandung Basin. The checkerboard pattern is not as well recovered outside the basin where the ray path coverage is sparse (Fig. S2 shows the Rayleigh ray path coverage at periods 1-8 ...
Citations
... Body wave information is typically challenging to extract from ambient noise, so most studies are restricted to the use of surface waves, which can provide good horizontal resolution, but depth resolution is limited. Moreover, the exploitation of group and phase velocity dispersion means that Swav e v elocity tends to be the final product of ANT, with P -wav e velocity being too poorly constrained by the data to permit retrie v al. Ambient noise and other surface wave imaging methods have been widely used in the Indonesian region, for example, Zulfakriza et al. ( 2014Zulfakriza et al. ( , 2020, Martha et al. ( 2017 ), Yudistira et al. ( 2021), Rosalia et al. ( 2022 and Pranata et al. ( 2020 ), but its application remains limited in Borneo, Makassar Strait and Sulawesi, with the exception of a focused study in nor ther n Bor neo (Greenfield et al. 2022 ). The aim of our study is to recover broad scale cr ustal str ucture through the determination of 3-D shear wave velocity in order to contribute to a better understanding of the complex tectonic setting of central Indonesia. ...
Borneo and Sulawesi are two large islands separated by the Makassar Strait that lie within the complex tectonic setting of central Indonesia. The seismic structure beneath this region is poorly understood due to the limited data availability. In this study, we present Rayleigh wave tomography results that illuminate the underlying crustal structure. Group velocity is retrieved from dispersion analysis of Rayleigh waves extracted from the ambient noise field by cross-correlating long-term recordings from 108 seismic stations over a period of 8 months. We then produce a 3-D shear wave velocity model via a two-stage process in which group velocity maps are computed across a range of periods and then sampled over a dense grid of points to produce pseudo-dispersion curves; these dispersion curves are then separately inverted for 1-D shear wave velocity (Vs), with the resultant models combined and interpolated to form a 3-D model. In this model, we observed up to ± 1.2 km/s lateral Vs heterogeneities as a function of depth. Our models illuminate a strong low shear wave velocity (Vs) anomaly at shallow depth (≤ 14 km) and a strong high Vs anomaly at depths of 20 – 30 km beneath the North Makassar Strait. We inferred the sediment basement and Moho depth from our 3-D Vs model based on iso-velocity constrained by the positive vertical gradient of the Vs models. The broad and deep sedimentary basement at ∼14 ± 2 km depth beneath the North Makassar Strait is floored by a shallow Moho at ∼22 ± 2 km depth, which is the thinnest crust in the study area. To the east of this region, our model reveals a Moho depth of ∼45 ± 2 km beneath Central Sulawesi, the thickest crust in our study area, which suggests crustal thickening since the late Oligocene. Moreover, the presence of high near surface Vs anomalies with only slight changes of velocity with increasing depth in southwest Borneo close to Schwaner Mountain (SM) confirm the existence of a crustal root beneath this region.
