Height of 3 floors = 12,9 meters = 35 pixels;
The width of the skyscraper = 475 pixels = 175 meters;
The width of the skyscraper = 120 pixels = 175 meters;
The height of the skyscraper = 360 pixels = 525 meters;
Volume = 16078125 m^3;
Buildings are usually 80% hollow.
True Volume = 16078125 * 0,2 = 3215625 m^3;
Weight of concrete is 2500 kg/m^3
Weight of steel is 7850 kg/m^3
According to our common feats page a ratio of 1/5 steel to concrete ratio is fine to use for buildings.
Mass of steel = 4207109375 kg;
Mass of concrete = 6699218750 kg;
Total Mass = 10906328125 kg;
Frequency of vibrations reaches from 0.2 to 33 Hz in ordinary earthquakes and up to 100 Hz in special cases. Since the shaking was strong and felt, I will use 33 Hz.
The formula for vibrations is "ω = Cyclic oscillation frequency = x * 3.14 * 33 Hz" where x is the amplitude.
Surface waves of earthquakes have an amplitude of several centimeters. Take 3 as a lowball.
v = Aω = 3*33*2*3.14 = 6,21 m/sec;
KE = (10906328125*6,21^2)/2 = 210296364223 Joules = 50 Tons TNT = 8-B;