Evaluation of Site Effects Using HVSR Measurements Along Srinagar Metro Alignment, Jammu and Kashmir

Abstract

Srinagar metro rail is set to be constructed as part of the Mass Rapid Transport System planned for the cities of Srinagar and Jammu in Jammu and Kashmir. In this paper, we present results of single station microtremor (MHVSR) tests conducted at 27 locations along the three corridors proposed in the project. Microtremor recordings were analysed using Nakamura’s horizontal-to-vertical spectral ratio (HVSR) method. The results reveal that the fundamental frequency (f0) at the sites ranges between 0.21 and 1.16 Hz with peak H/V amplitude 2.01–5.89. At many locations, more than one peak was observed in HVSR curves signifying the presence of multiple impedance contrasts within the subsurface. Low frequency peak indicates an impedance contrast at deep depths, whereas peak at higher frequencies indicates shallow impedance contrast. Further, the results are compared with Vs30 (average shear wave velocity over 30 m depth) obtained at the same sites in a previous study by our group. It was found that f0 and Vs30 do not follow a direct correlation at majority of the sites. Locations like Batpora, Soura, Hazratbal, and Osmanabad are found to have low f0, despite having high Vs30 and characterized as site classes C and D according to NEHRP guidelines. The study concludes that these apparent anomalies essentially indicate that Vs30 might not be an appropriate proxy for site amplification, as was also pointed out by Castellaro et al. (2008) and several other authors. Consequently, a new site characterization procedure must be adopted which incorporates other parameters in addition to Vs30. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.