Quito: A strong 7.8-magnitude earthquake struck off the coast of Ecuador on Saturday, the US Geological Survey (USGS) reported. No casualties were reported so far, but the tremor sent residents in the capital of Quito streaming into the streets, and some parts of the capital were without power or telephone service, Xinhua news agency reported. The quake was also strongly felt in several other Ecuadorian cities. Local media reported that at least one house and an overpass had collapsed in the port city of Guayaquil. The quake was centered just off the coast at a shallow depth of 19 km, according to the USGS, which originally put the quake at a magnitude of 7.4 and then raised it to 7.8. Ecuador's Institute of Geophysics put the quake's magnitude at 6.5 and the depth at 10 km. The Pacific Tsunami Warning Centre said hazardous tsunami waves are possible for some coasts. Ecuador is located in a region with frequent volcanic eruptions and earthquakes.