Pakistan, June 4 -- The earth beneath Karachi continues to stir, not with a roar but with a series of unnerving shivers. Nineteen tremors in less than four days, the strongest a modest magnitude 3.6. It is not a disaster per se, and Sindh Chief Minister Murad Ali Shah may even be right in suggesting that low-intensity tremors can alleviate tectonic stress and potentially prevent bigger earthquakes. However, for a city long lulled into seismic complacency, these recent events should serve as a reminder of the looming catastrophe that awaits, not if but when the ground decides to assert its power.

Karachi, a sprawling megacity of 22 million, sits precariously. Geologists may describe its seismic margin as "passive," yet its proximity to th...