M7.1 earthquake 9 km S of Stara Zagora, Bulgaria

Saturday, April 14, 1928, 09:00:00 UTC · 42.351°N, 25.641°E

A magnitude 7.1 earthquake struck 9 km S of Stara Zagora, Bulgaria on Saturday, April 14, 1928, 09:00:00 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M7.2 on August 9, 1912.

Magnitude: 7.1; Major · mw
Depth: 10 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VIII; Severe (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

674 kilotons of TNT

That is about 45 times the Hiroshima bomb. It released about 1,413 times the energy of a magnitude 5.0.

Tectonic setting

214 km

from the nearest mapped plate boundary, between the Anatolian and Eurasian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

10 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 200 km

USGS lists 7 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M7.1 on April 18, 1928. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 20 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 24 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2,952 recorded deaths. The most severe:

1912M7.2
Marmara Sea
9 Aug 1912 · 218 km away
2,800 deathsExtreme damage ($25M+)tsunami
1928M6.8
Chirpan
14 Apr 1928 · 33 km away · intensity X
127 deathsExtreme damage ($25M+)
1905M7.2
Aegean Sea
8 Nov 1905 · 265 km away · intensity X
11 deathsModerate damage ($1–5M)tsunami
1902M6.5
Thessaloniki
5 Jul 1902 · 275 km away · intensity IX
5 deathsModerate damage ($1–5M)tsunami
1901M7.2
Balchik
31 Mar 1901 · 261 km away · intensity X
4 deathsSevere damage ($5–24M)tsunami
1901M6.4
Balchik, Kavarna, Blatnitsa, Limanu
31 Mar 1901 · 275 km away · intensity VIII
4 deathsSevere damage ($5–24M)

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers