Reviewed by USGSBulgaria99y ago
M7.1 earthquake 3 km W of Brezovo, Bulgaria
Wednesday, April 18, 1928, 19:22:56 UTC · 42.351°N, 25.044°E
A magnitude 7.1 earthquake struck 3 km W of Brezovo, Bulgaria on Wednesday, April 18, 1928, 19:22:56 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M7.1 on April 14, 1928.
- 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
235 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 5 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.8 on April 25, 1928. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 5.65 km NNW of Asenovgrad, Bulgaria99y ago · 36 km SW of this epicenter
- 5.84 km NW of Simeonovgrad, Bulgaria99y ago · 70 km SE of this epicenter
- 5.28 km NNE of Dimitrovgrad, Bulgaria99y ago · 54 km SE of this epicenter
- 5.114 km N of Chirpan, Bulgaria99y ago · 22 km E of this epicenter
- 5.819 km SSE of Pavel Banya, Bulgaria99y ago · 23 km NE of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 25 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.2Aegean SeaNovember 8, 1905 · 254 km S of this epicenter
- 7.225 km SE of Malkara, TurkeyAugust 9, 1912 · 250 km SE of this epicenter
- 7.19 km S of Stara Zagora, BulgariaApril 14, 1928 · 49 km E of this epicenter
- 7.07 km SE of Stara Kresna, BulgariaApril 4, 1904 · 162 km SW of this epicenter
- 6.86 km W of Stara Kresna, BulgariaApril 4, 1904 · 171 km W of this epicenter
- 6.730 km SW of Kumbağ, TurkeySeptember 13, 1912 · 258 km SE of this epicenter
- 6.75 km NNE of Lyaskovets, BulgariaJune 14, 1913 · 106 km NE of this epicenter
- 6.223 km NE of Biga, TurkeyAugust 10, 1912 · 293 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 23 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2,944 recorded deaths. The most severe:
- 1912M7.2
Marmara Sea
9 Aug 1912 · 250 km away
2,800 deathsExtreme damage ($25M+)tsunami
- 1928M6.8
Chirpan
14 Apr 1928 · 27 km away · intensity X
127 deathsExtreme damage ($25M+)
- 1905M7.2
Aegean Sea
8 Nov 1905 · 254 km away · intensity X
11 deathsModerate damage ($1–5M)tsunami
- 1902M6.5
Thessaloniki
5 Jul 1902 · 238 km away · intensity IX
5 deathsModerate damage ($1–5M)tsunami
- 1893M6.5
Samothraki
9 Feb 1893 · 209 km away · intensity X
1 deathModerate damage ($1–5M)tsunami
- 1928M7.0
Popovitsa
18 Apr 1928 · 28 km away · intensity XI
Extreme damage ($25M+)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.