What they did not expect was for the menace to come from the earth rather than the sky.

The strong 6.4-magnitude earthquake that rocked Puerto Rico on Tuesday plunged almost the entire island into a blackout similar to the one following Maria, reduced some homes to rubble and triggered new fears that the government would find itself overwhelmed by catastrophe. It was the second big quake in two days.

Unable to catch a break from Mother Nature, few Puerto Ricans expressed confidence that public officials would protect them from new powerful quakes or the devastation they could cause. A United States commonwealth facing crushing debt and bankruptcy, on the heels of a political upheaval that ousted two governors last summer, found itself asking: Again?

“I prefer Maria,” declared Nicole Santos Torres, 21, Ms. Torres’s daughter, as she sat surrounded by relatives outside the Juan “Pachín” Vicéns Auditorium in Ponce, the biggest city in southern Puerto Rico, the region most affected by the quake.

A few people in a red Jeep distributed food late on Tuesday afternoon, the only thing many evacuees had eaten all day. Everything in the city was closed, leaving the streets dark and deserted, even of the police.