TEHRAN — A powerful earthquake that struck southeastern Iran was felt in several countries in Asia on Tuesday, rocking buildings in the Indian capital of New Delhi, sending panicked resident of Karachi, Pakistan, fleeing into the streets and causing tremors through Persian Gulf states. Iranian officials said they expected many deaths. The earthquake measured 7.8 on the Richter scale and its epicenter was near Khash, Iran, not far from Iran’s border with Pakistan, the United States Geological Survey said. An Iranian official told state television that he expected hundreds of deaths because of the severity of the earthquake.