RIDGECREST, Calif. — Crews in Southern California assessed damage to cracked and burned buildings, broken roads, leaking water and gas lines and other infrastructure Saturday after the largest earthquake the region has seen in nearly 20 years jolted an area from Sacramento to Las Vegas to Mexico.

No fatalities or major injuries were reported after Friday night’s 7.1-magnitude earthquake. But warnings by seismologists that large aftershocks were expected to continue for days — if not weeks — prompted further precautions.

The California National Guard was sending 200 troops, logistical support and aircraft, said Maj. Gen. David Baldwin. The Pentagon had been notified, and the entire California Military Department was put on alert, he said.

The quake struck at 8:19 p.m. Friday and was centered 11 miles (18 kilometers) from Ridgecrest, the same area of the Mojave Desert where a 6.4-magnitude temblor hit just a day earlier.

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