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The Lonar impact crater in the Deccan Volcanic Province of India is an excellent analogue for impact-induced structures on the Moon and other terrestrial planets. We present a detailed architecture of the crater using a high-resolution 3-D seismic velocity image to a depth of 1.5 km through the inversion of high-frequency ambient noise data recorded over 20 broad-band seismographs operating around the crater. The ambient noise waveform is dominated by cultural noise in the 1–10 Hz band. The shear wave velocity (Vs) model is created from Rayleigh wave group velocity data with a horizontal resolution of 0.5–1 km in the period range of 0.1–1.2 s. A key feature of the model is a velocity reduction of 10–15 per cent below the crater compared to outside the ejecta zone. The low-velocity zone below the crater is nearly circular and extends to a depth of ∼500 m. This estimated crater's depth is consistent with global depth–diameter scaling relations for simple craters. The basement, with a Vs of more than 2.5 km s−1, lies beneath the Deccan basalt, which has a Vs of ∼2.4 km s−1. These results are consistent with laboratory-measured data from the Lonar crater and borehole data in the western Deccan trap. This study opens a new window for exploring impact craters and sub-basalt structures using high-frequency ambient noise tomography. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of Rayleigh wave group velocity tomography in SouthIndia. South India is a stable continent comprising of Precambrian terrains such as the easternDharwar craton (EDC), the western Dharwar craton (WDC), the southern Granulite terrain(SGT), and the Cuddapah basin. The data used for analysis were recorded at 51 broadbandstations operated during 2009-2012 across this region. Based on the analysis a total of781 unique earthquake events with shallow to moderate depths were chosen. Theepicentral distance was from 5o-30o and magnitude Ms >= 4.5. This attributedto a total of 4873 source-station raypaths for which the dispersion curves werecalculated to obtain Rayleigh-wave group velocity maps for time periods from10-200 secs. Due to the high ray coverage over the southern terrain, we obtained ahigh resolution of 0.5o-1o across all time periods. The tomographic velocity mapsshow a thinner crust (∼35 Km) in the late Archean (∼2.7 Ga) EDC and relativelyhigher (∼40-50 Km) in adjoining terrains (mid-Archean and Proterozoic). Themid-Archean (∼3.36 Ga) WDC has a thicker crust (∼50 Km). Furthermore, the local groupvelocity dispersion curve obtained for each grid cell from 10-200 seconds wereinverted for shear wave velocity models. The shear wave velocity models gave aquantitative image of the crust as well as the lithospheric root. The mid-ArcheanWDC has a thicker lithosphere with lithosphere-asthenosphere(LAB) around anaverage of 160-180 Km. The southern root of the lithosphere of WDC continued tillnorthern province of SGT which showed higher LAB compared to the thickness in therest of SGT (∼140 Km). The LAB in late Archean EDC along with the Cuddapahprovince was found to be flat and thinner (∼140-160 Km) compared to WDC. Thecoastal areas showed a thin LAB (∼110-130 Km) except in the WDC boundary. Thesouthernmost tip showed a very thin LAB (100-110 Km). This observation suggests thatthe average crustal and lithospheric thickness of WDC is more compared to theEDC. This can infer that the WDC after it’s cratonization has remained mostlyinert, while EDC might have undergone tectonothermal changes in the Proterozoic. [ABSTRACT FROM AUTHOR]