Strong ground motions from two moderate size (Mw5.5) Kachchh intraplate earthquakes, Gujarat, India

Data from 16-18  strong-motion accelerograph sites enabled us to estimate strong motion parameters so that the suitability of the design response spectra of BIS (criteria for earthquake-resistant design of structures, part I—general provisions and buildings, Bureau of Indian Standards, 2002) in Kachchh, Gujarat can be examined. Our study reveals that the estimated normalized response spectra at strong-motion accelerograph sites, which are lying in tertiary formations or near a zone of geological contact between Jurassic and tertiary formations, exceeded the design response spectra at 0.07–0.2 s, correlating with complete collapse of low-rise buildings, water tanks and dams in the area during the 2001 Bhuj earthquake. On the other hand, the normalized acceleration spectrum of hard sediment (rock site) is found to not exceeding the design spectrum, correlating with the lack of damage in the Mesozoic hill zone. The estimated normalizedmacceleration spectra at SMA sites lying on hard sediments of Jurassic/Mesozoic formations are found to be lower than the design spectra, which suggests that these stations are less hazardous. We also notice that spectral acceleration values at few sites lying on quaternary formations have exceeded the design spectra at 3–4 s, suggesting these sites hazardous for engineered reinforced structures like bridges. We propose that the design spectra for the Kachchh region, Gujarat, India, should be modifed incorporating local site, path and source effects.

Figure Caption: Location of study area

 

Citation: Mandal P.; 2020, Strong ground motions from two moderate size (Mw5.5) Kachchh intraplate earthquakes, Gujarat, India, Natural Hazards, https://doi.org/10.1007/s11069-020-04092-8 external link