Why was second 7.5 magnitude quake in Venezuela nearly 3 times more powerful than first?

Two powerful earthquakes of magnitude 7.2 and 7.5 struck Venezuela just 40 seconds apart. Earthquake magnitudes are measured on a logarithmic scale, where each increase represents a substantial jump in energy release. Because of this, the second earthquake released nearly three times the energy of the first. As a result, it caused much stronger ground shaking and greater structural damage.