Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
DEPARTMENT OF CIVIL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY BOMBAY Geotechnical Earthquake Engineering Quiz Full Marks – 100 Duration – One (1) Hour Answer ALL Questions Assume reasonable data if required ========================= 1 1. The seismicity of a particular region is described by the Gutenberg-Richter recurrence law as: log λm = 4.0 – 0.72M (a) What are the probabilities that at least one and exactly one earthquake of magnitude greater than 6.5 will occur in (i) 10 year period (ii) 50 year period and (iii) 150 year period? (b) Determine the would have a 10% at least once in a nomenclature of (10+20 = 30) earthquake magnitude that probability of being exceeded 50 year period. What is the this level of earthquake? 2 2. Using probabilistic seismic hazard curve, for λm = 0.1, amax = 0.27g. Compute the probability of exceeding this maximum seismic acceleration in 50 years and 150 years period and the corresponding equivalent maximum value of the earthquake magnitude using Gutenberg and Richter Recurrence Law for worldwide data (Circumpacific belt). (20) 3 3. In a field test, primary wave velocity of a sandy soil with Poisson’s ratio = 0.3, unit weight = 17 kN/m3 is obtained as 400 m/s. Estimate shear wave (S-wave) velocity propagating through that soil layer. Calculate the maximum shear modulus of the soil. If this soil layer with 8% damping and of 10 m thickness is located between the ground surface and rigid bed rock, compute the amplification of bed rock spectral acceleration of an earthquake of 1.5 Hz frequency which will be felt at the ground surface. (30) 4. Among different types of body waves, which one is having largest shadow zone and why? 4 Distance between two seismographic stations X and Y is 196 km on a level ground. A shallow earthquake occurred with the epicenter Z, which is estimated at 56 km from station X and Z is located exactly on the line joining two stations X and Y. The recorded difference in arrival time between P and S wave was 20 seconds at station Y. Estimate the difference in arrival time between P and S waves at station X. If velocity of S wave is half of the velocity of P wave. Estimate the crustal velocities of P and S waves for this earthquake. (5+15 = 20) END 5