FACTBOX: Five facts on Indonesia's Padang and Sumatra

(Reuters) - Rescue teams struggled on Thursday to find people trapped under debris after a powerful earthquake hit the Indonesian city of Padang, possibly killing thousands.

A second quake, of magnitude 6.6, hit another part of Sumatra island on Thursday, causing fresh panic.

Following are five facts on Padang and Sumatra:

* A port city of 900,000 people and the capital of West Sumatra province, Padang lies on a coastal plain and is surrounded by steep mountains that stretch far inland. Padang food, consisting of dozens of small bowls of various spicy curries and other dishes, is popular across Indonesia Textiles and rubber are among the area's important businesses. Two strong earthquakes there in March 2007 killed at least 72 people.

* Padang is on the west coast of Sumatra, which is the world's fifth-biggest island with a population of some 48 million and covering an area of 470,000 sq km (181,000 square miles). Sumatra is a significant source of rubber, palm oil, timber, coffee and other agricultural commodities, as well as coal, oil, natural gas, tin and other minerals.

* Like most of Indonesia, Sumatra lies along the so-called Pacific "Ring of Fire" of major seismic and volcanic activity and one of the world's most active fault lines, where the Indo-Australia continental plate grinds against the Eurasia plate. Geologists have long warned Padang may one day be destroyed by a huge earthquake because of its location.

* Aceh province on Sumatra's northern tip was hardest hit by the 2004 tsunami that killed 230,000 people in the Indian Ocean area. Some 170,000 of those deaths were in Indonesia, mostly in Aceh. Many of the province's coastal cities and towns were left as little more than piles of rubble.

* Poor infrastructure, warning systems still being refined and improved, and often shoddy construction in Sumatra as in much of Indonesia mean seismic and volcanic events there frequently cause more deaths and damage than the equivalents in strength in more developed countries such as Japan.

(Writing by Jerry Norton; Editing by Ed Davies)