"In terms of magnitude, they were mini earthquakes. They equaled the energy of a micro-scale earthquake," Dogan Kalafat of the Kandilli seismological institute told the Anatolia news agency on Friday.
The observatory, which is situated about 10 kilometers from both bomb sites, measured the magnitude of the blast at the HSBC bank as 1.4 on the Richter scale and the second one at the British consulate as 1.3, he said.
He said however that the force of the explosions in the immediate vicinity of the bomb sites in the European part of the city could have equaled the impact of a strong earthquake ranking about 5.0 on the Richter scale.
The attacks, which officials say were carried out by suicide truck drivers, claimed at least 27 lives, just days after another 25 people perished in similar car bombings at two synagogues in the city.
Many said after the explosions they felt the city had been hit by earthquakes. The city, which is situated near a seismological faultline, is expected to be hit by a major tremor in the next three decades.
Turkey is notorious for its active faultlines, including the North Anatolian Fault, which crosses from east to west.