WASHINGTON, Jan. 9 (Xinhua) -- An underwater earthquake of magnitude 6.4 on the Richter scale struck 240 km off the coast of Oregon at 5:37 p.m. Wednesday (0137 GMT Thursday), according to U.S. Geological Survey (USGS).

    "So far we have had no reports that the earthquake has even been felt," Bruce Presgrave of the USGS told KNX News, a radio channel in Oregon.

    "The tsunami warning centers have not issued any warning for this event," he added.

    The mechanism of this quake, the manner in which it shook, was horizontal, making it unlikely to produce a tsunami, according to Presgrave.

    There is also no report of damage or casualty related to the quake.