A strong earthquake with a preliminary magnitude of 5.4 struck off southern Greece Monday but no injuries or damage were reported, Greek authorities said. A smaller quake was also felt later in the day near the country's second-largest city,Thessaloniki, but it also caused no damage or injuries. The Athens University's Geodynamic Institute said the first, undersea quake occurred at 0514GMT (8:14 a.m. local time) off the southwestern tip of the Peloponnese. It had a depth of 10 kilometers (6 miles). The second quake, with a preliminary magnitude of 4.2, hit at 0821GMT (11:21 a.m. local time), according to Thessaloniki University's Geodynamic Institute. Its epicenter was about 30 kilometers (18 miles) north-northeast of Thessaloniki, between the villages of Askos and Evangelismos. Greece occupies one of the most earthquake-prone areas of the world, registering scores of quakes every day. Most are not even felt, and ones causing severe damage, or loss of life, are rare. In 1999, a magnitude-5.9 earthquake on the fringes of Athens killed 143 people.