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Magnitude 4.0 earthquake strikes off Silivri coast, felt across Istanbul

A 4.0 earthquake struck off the coast of Silivri in the Marmara Sea on Wednesday, according to Kandilli Observatory. The tremor occurred at 12:13 p.m. local time at a depth of 6.99 kilometers (4.34 miles).

Türkiye's Disaster and Emergency Management Authority (AFAD), which also monitors seismic activity in the region, reported the magnitude as 3.9.

The tremor was felt across much of Istanbul, causing brief concern among residents. There have been no immediate reports of damage or injuries. Authorities continue to monitor the situation.

A CNN Turk reporter shared real-time updates on the earthquake:

There are reports from people who felt the tremor, particularly in the Silivri and Buyukcekmece areas.

While we are currently in Caglayan and did not feel it here, it's reported that the earthquake was felt in districts closer to Silivri, especially in Catalca.

Coastal areas seem to have experienced the tremor as well.

Local residents wait in a street in Istanbul following an initial 4.0 earthquake at 12:49 pm (9:49 a.m. GMT), followed by three others with magnitudes of 4.4 to 4.9, Türkiye, April 23, 2025. (AFP Photo)

Second earthquake with 6.2 magnitude hits Istanbul on April 23

After the first earthquake, a stronger earthquake struck Istanbul on Wednesday at around 12:50 p.m. local time.

AFAD announced that a 6.2 magnitude earthquake had struck off the coast of Silivri, Istanbul, at 12:49 p.m.

According to the information contained in the report, the epicenter is located in the Marmara Sea, Silivri district of Istanbul, where a 6.2 magnitude tremor was recorded.

It was determined that the earthquake, which was felt in the surrounding provinces as well as Istanbul, occurred at a depth of 6.92 kilometers.

Just moments after the 6.2 quake, a third tremor followed. At 12:51:20 p.m. local time, a 4.4 magnitude earthquake struck the Marmara Sea, approximately 14.74 kilometers off the coast of Buyukcekmece, Istanbul.

The tremor occurred at a depth of 7 kilometers and further intensified the alarm in the region.

Local residents wait in a street in Istanbul following an initial quake at 12:49 pm (0949 GMT), followed by three others with magnitudes of 4.4 to 4.9, Türkiye, April 23, 2025. (AFP Photo)

Timeline after initial 4.0 earthquake in Istanbul on April 23:

Seismologists confirmed that the April 23 event was part of a rapid seismic sequence affecting the Marmara region.

The initial tremor was followed by several aftershocks in quick succession, all recorded within a single hour.

12:19 p.m. – 3.9 magnitude foreshock
12:49 p.m. – 6.2 magnitude mainshock
12:51 p.m. – 5.9 and 4.4 magnitude tremors
1:01 p.m. – 4.8 magnitude
1:02 p.m. – 4.5 and 4.9 magnitudes
1:07 p.m. – 3.4 magnitude aftershock

The clustering of these tremors raised alarm across Istanbul, particularly in districts near the fault line.

Local residents wait in a street in Istanbul following an initial quake at 12:49 pm (9:49 a.m. GMT), followed by three others with magnitudes of 4.4 to 4.9, Türkiye, April 23, 2025. (AFP Photo)

Areas most at risk in Istanbul during a strong earthquake

There are districts in Istanbul that are vulnerable in terms of geological structure and urban development.

Zeytinburnu
Fatih (Historical Peninsula)
Bakirkoy
Avcilar (especially coastal areas and near Kucukcekmece Lake)
Kucukcekmece (Menekse, Kanarya, Cumhuriyet neighborhoods)
Beylikduzu (Gurpinar: Pekmez and Pinarkent neighborhoods)
Buyukcekmece (Devebagirtan region)
Kumburgaz and Silivri

These zones are marked by loose soil, landslide-prone terrain, and dense construction near the Marmara fault line.

Safer zones in Istanbul in terms of ground stability include:

Kadikoy
Camlica
Aydos
Upper parts of Kartal and Maltepe

The 6.2 magnitude earthquake off Silivri has prompted immediate government response and technical evaluations across transport, infrastructure, and housing. Metro operations remain stable, and aftershocks are being tracked closely by seismic experts.

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