A strong earthquake measuring 6.2 on the Richter scale struck near Istanbul on Wednesday afternoon, followed by an aftershock of 5.5.

According to local media, the quake was felt in surrounding provinces as well as in Istanbul.

Another earthquake had occurred half an hour earlier, causing concern in Eastern Thrace and also being felt in parts of Istanbul.

That earlier quake measured 3.9 on the Richter scale, located in the Sea of Marmara, between Tekirdağ (Raedestos) and Istanbul. According to AFAD (Turkey’s Disaster and Emergency Management Authority), the quake had a focal depth of 6.9 kilometers.