By Vivian Sequera and Mayela Armas CARACAS, June 25 (Reuters) - Thousands of Venezuelans were feared dead on Thursday after two powerful earthquakes wreaked havoc in and around the capital Caracas, trapping people beneath the rubble of collapsed buildings and setting off powerful aftershocks. A magnitude 7.2 earthquake hit about 160 km (100 miles) west of Caracas on Wednesday afternoon, followed less than a minute later by a magnitude 7.5 tremor, according to the U.S. Geological Survey.