Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Acta Geophysica

2 2023

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Shear wave velocity structure beneath the eastern Indian Ocean from Rayleigh wave dispersion measurements

Rehman Haseeb, Sharma Jyoti, Subrahmanyam Mangalampalli, Begum Shaik Kareemunnisa

Acta Geophysica

2023

Vol. 71, no. 3

1187--1201

The Eastern Indian Ocean is a tectonically and geodynamically active region that has experienced deformations due to rifting, uplifting, and plume activity. The earlier Rayleigh wave studies in the East Indian Ocean were mainly focused on the structure of the Bay of Bengal, Ninety East Ridge, and Broken Ridge. The structure of other region of the East Indian Ocean is not much explored. In the present study, Rayleigh wave dispersion analysis is performed to observe the signatures of upper mantle deformation in terms of shear wave velocity of the East Indian Ocean using global search method. The fundamental mode Rayleigh wave group velocities are estimated between 15 and 100 s using the multiple filter technique. The group velocities of the raypaths that traverse the same region are clustered (E1–E8) to get an average dispersion curve. Using a genetic algorithm, each cluster's group velocities are inverted for shear velocity structure. The observed dispersion curve of E6, E7, and E8 indicates the lower group velocities between 35 and 100 s relative to E1, E2, E3, E4, and E5, with an average variation of about 0.07–0.18 km/s. The crustal thickness obtained in the study region is ~ 26 km and is due to the increased thickness of the lower crust (9.1–12.4 km) having Vs 3.95–4.04 km/s. The theoretical Vs have been calculated for serpentinite rock at uppermost lithospheric conditions and found to be similar to the Vs of the lower crust in the present study. Hence, it is assumed that unusual crustal thickness is due to the progressive development of the upper lithosphere formation (Ultramafic rock) into material (serpentinite rock) with crustal-like shear velocity or moderately lower than sub-Moho shears velocity. The undeformed lithosphere is evidenced by the high-velocity (Vs 4.62–4.77 km/s) layer beneath the Moho, whose thickness ranges from 41.3 to 51.6 km. The high-velocity lithosphere is followed by a low-velocity zone that extends up to 160 km; however, the variation in Vs (4.57–4.31 km/s) indicates that the low-velocity zone is deformed.

Investigation of groundwater potential zones in hard rock terrains along EGMB, India, using remote sensing, geoelectrical and hydrological parameters

Rao Palavai Venkateswara, Subrahmanyam Mangalampalli, Raju Bakuru Anand Gajapathi

Acta Geophysica

2023

Vol. 71, no. 4

1867--1883

The research region is located in hard rock terrains of the Eastern Ghats mobile belt in East Godavari district of Andhra Pradesh state, India, and it occupies an area of 2645.3 sqkm. The rocks of this region are complex granite gneiss and khondalites. The people living this region are facing sever water problem. The objective of this research is to investigate the location of groundwater potential zones (GWPZs) as the region is hard rock terrain, and weathering or fracturing of rocks is the only source of groundwater. Electrical resistivity values alone may not be sufficient for locating the GWPZ. Therefore, in order to locate GWPZ of the study area precisely, remote sensing and Dar-Zarrouk parameters are more useful. From the analysis of remote sensing imageries, surface geomorphological features and lineaments have been identified. These features control the storage and movement of groundwater in complex hard rock terrains. Dar-Zarrouk characteristics have been used to explore hydrodynamic parameters (hydraulic conductivity and transmissivity), which determine the aquifer potentiality of an area. Based on the values of transmissivity together with lithologic data, the study area has been divided into four categories of groundwater potential as high, moderate, low, and negligible. In most of the study area, the availability of groundwater is moderate (Transmissivity—50–500 m2/day). At a few locations (about 46) of the hard rock region, the transmissivity is high (> 500 m2/day). However, almost all the locations surveyed in sedimentary formations are found to be good potential of groundwater.