Wyniki wyszukiwania - Biblioteka Nauki

1

Crustal thickness and poisson’s ratio variations across the northwest Himalaya and eastern Ladakh

100%

Hazarika D. , Kumar N. , Yadav D.

Acta Geophysica

|

2013

|

tom Vol. 61, no. 4

905--922

EN

Crustal thickness and PoissonPoisson's ratios are estimated across the northwest (NW) Himalaya and eastern Ladakh applying H-k stacking method on receiver functions of teleseismic earthquakes recorded at 16 broadband seismological stations. The results show significant lateral variation of crustal thickness from the Lesser and Higher Himalaya (~50 km thick) to Ladakh (~80 km thick) through the Indus Tsangpo Suture Zone (ITSZ). The Indian Moho is continuously traceable across the ITSZ which is consistent with the underthrusting of the Indian plate beyond the surface collision boundary. The estimated Poisson's ratio is intermediate in the Tethyan Himalaya (0.269-0.273) and high beneath Ladakh (0.280-0.303), indicating the effect of aqueous fluid/partial melt present in the crust.

2

HSPB seismic broadband station in Southern Spitsbergen: First results on crustal and mantle structure from receiver functions and SKS splitting

88%

Wilde-Piorko M. , Grad M. , Wiejacz P. , Schweitzer J.

|

2009

|

tom 30

|

nr 4

301-316

3

Crustal velocity structure in Borneo Island using receiver function inversion

75%

Syuhada S. , Pranata B. , Anggono T. , Ramdhan M. , Zulfakriza Z. , Febriani F. , Prasetio A. D. , Dewi C. N. , Hasib M. , Sulaiman A.

Acta Geophysica

|

2022

|

tom Vol. 70, no 6

2529--2553

EN

Borneo is an island situated in a tectonically complex region and characterised by multiple arcs and continental blocks accreted during the Mesozoic and early Cenozoic. We analyse receiver functions of teleseismic events from 12 seismic stations around the island. In general, these stations sample a variety of geological environments, including Meratus Complex, Eastern Borneo, South–Western Borneo, North–Western Borneo, and Sabah Zones. We then derive the shear wave velocity models from the inversion of receiver functions using the stochastic non-linear approach. Inversion results indicate that the island is covered by sedimentary layers with thickness ranging from 1 to 3 km thick. The inversion solutions for most stations also show that the crustal thickness varies between 26 and 36 km around the region. The variation in the average crustal Vp/Vs values obtained for each seismic station addresses the geological diversity of the study area. Furthermore, the lowvelocity zone with high and low Vp/Vs in the lower crust observed beneath some seismic stations may be associated with the tectonic evolution and development of Borneo Island. The results inferred from our inversion are generally consistent with other previous geological and geophysical studies conducted in this region.

4

S-velocity structure beneath the Bohemian Massif from Monte Carlo inversion of seismic receiver function

75%

Trojanowski J. , Wilde-Piórko M.

Acta Geophysica

|

2012

|

tom Vol. 60, no. 1

76-91

EN

The paper contains an analysis of S-velocity distribution in the crust and upper mantle beneath the Bohemian Massif, which is the second biggest Variscan outcrop in Europe. It occupies mainly the west part of Czech Republic and also part of south-west Poland and south-east Germany. We use data from 10 permanent stations set in the region. Some previous papers relate to the same scope but use linear methods to inverse receiver function. Our new approach involves Monte Carlo techniques for inversion procedure, which is more convenient and robust for such a non-linear task. The result of Monte Carlo inversion is compared with the previously achieved one. The obtained Moho depths vary from 29 km in the north-west part of the Bohemian Massif to 38 km in the south and south-east and are consistent with other papers. Some discrepancies occur in the middle and upper crust.

5

Crustal Structure Along Sunda-Banda Arc Transition Zone from Teleseismic Receiver Functions

75%

Syuhada S. , Hananto N. D. , Abdullah C. I. , Puspito N. T. , Anggono T. , Yudistira T.

Acta Geophysica

|

2016

|

tom Vol. 64, no. 6

2020--2050

EN

We analyzed receiver function of teleseismic events recorded at twelve Indonesian-GEOFON (IA-GE) broadband stations using nonlinear Neighbourhood Algorithm (NA) inversion and H-k stacking methods to estimate crustal thickness, Vp/Vs ratios and S-wave velocity structure along Sunda-Banda arc transition zone. We observed crustal thickness of 34-37 km in Timor Island, which is consistent with the previous works. The thick crust (> 30 km) is also found beneath Sumba and Flores Islands, which might be related to the arc-continent collision causing the thickened crust. In Timor and Sumba Islands, we observed high Vp/Vs ratio (> 1.84) with low velocity zone that might be associated with the presence of mafic and ultramafic materials and fluid filled fracture zone. The high Vp/Vs ratio observed at Sumbawa and Flores volcanic Islands might be an indication of partial melt related to the upwelling of hot asthenosphere material through the subducted slab.

6

Lithospheric structure of the Arabian Shield from joint inversion of P- and S-wave receiver functions and dispersion velocities

51%

Al-Amri A. M.

Acta Geologica Polonica

|

2015

|

tom Vol. 65, no. 2

227--243

EN

New velocity models of lithospheric thickness and velocity structure have been developed for the Arabian Shield by three tasks: 1) Computing P-Wave Receiver Functions (PRFs) and S-Wave Receiver Functions (SRFs) for all the broadband stations within the Saudi seismic networks. The number of receiver function waveforms depends on the recording time window and quality of the broadband station. 2) Computing ambient noise correlation Green’s functions for all available station pairs within the Saudi seismic networks to image the shear velocity in the crust and uppermost mantle beneath the Arabian Peninsula. Together they provided hundreds of additional, unique paths exclusively sampling the region of interest. Both phase and group velocities for all the resulting empirical Green’s functions have been measured and to be used in the joint inversion. 3) Jointly inverted the PRFs and SRFs obtained in task 1 with dispersion velocities measured on the Green’s functions obtained in task 2 and with fundamental-mode, Rayleigh-wave, group and phase velocities borrowed from the tomographic studies to precisely determine 1D crustal velocity structure and upper mantle. The analysis of the PRFs revealed values of 25 - 45 km for crustal thickness, with the thin crust next to the Red Sea and Gulf of Aqaba and the thicker crust under the platform, and Vp/Vs ratios in the 1.70 – 1.80 range, suggesting a range of compositions (felsic to mafic) for the shield’s crust. The migrated SRFs suggest lithospheric thicknesses in the 80-100 km range for portions of the shield close to the Red Sea and Gulf of Aqaba and near the Arabian Gulf. Generally, the novelty of the velocity models developed under this paper has consisted in the addition of SRF data to extend the velocity models down to lithospheric and sub-lithospheric depths.