An earthquake measuring 5.1 on the Richter Scale shook the Japanese capital Tokyo and its environs Wednesday evening, Deutsche Presse Agentur (dpa). There were no immediate reports of casualties or damage. No tsunami warning was given. The centre of the quake lay around 110 kilometres underground in the neighbouring province of Chiba. Japan is one of the most earthquake-prone countries in the world. --SP 23 09 Local Time 20 09 GMT