Reviewed by USGSPhilippines50y ago
M5.5 earthquake 6 km SSE of Sapad, Philippines
Friday, September 10, 1976, 14:50:11 UTC · 7.797°N, 123.847°E
A magnitude 5.5 earthquake struck 6 km SSE of Sapad, Philippines on Friday, September 10, 1976, 14:50:11 UTC, at a depth of 53.0 km (shallow). It is the strongest earthquake within 300 km since an M5.8 on August 23, 1976.
- Magnitude
- 5.5
- Moderate · mb
- Depth
- 53 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- IV
- Light (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 75 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
3 kilotons of TNT
That is about 1/6 of the Hiroshima bomb. It released about 6 times the energy of a magnitude 5.0.
Tectonic setting
369 km
from the nearest mapped plate boundary, between the Philippine Sea and Sunda plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
53 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 75 km
USGS lists 3 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.3 on September 11, 1976. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 186 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.31918 Mindanao, Philippines EarthquakeAugust 15, 1918 · 252 km S of this epicenter
- 8.11924 Mindanao, Philippines EarthquakeApril 14, 1924 · 287 km SE of this epicenter
- 7.919 km WNW of Palimbang, PhilippinesAugust 16, 1976 · 172 km S of this epicenter
- 7.410 km ESE of Basak, PhilippinesDecember 19, 1928 · 129 km S of this epicenter
- 7.4Mindanao, PhilippinesMarch 31, 1955 · 78 km W of this epicenter
- 7.312 km SSW of Kipit, PhilippinesOctober 20, 1942 · 153 km W of this epicenter
- 7.25 km ESE of Veruela, PhilippinesJune 13, 1929 · 239 km E of this epicenter
- 7.25 km NW of Kadingilan, PhilippinesMarch 2, 1923 · 114 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 32 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 8,660 recorded deaths. The most severe:
- 1976M8.0
Mindanao: S
16 Aug 1976 · 169 km away · intensity VI
8,000 deaths$134 million damagetsunami
- 1955M7.4
Mindanao: Lanao,Ozamiz,Cotabato
31 Mar 1955 · 78 km away · intensity VIII
465 deaths$5 million damagetsunami
- 1928M7.4
Cotabato,N Coast Of Illana Bay
19 Dec 1928 · 129 km away · intensity VII
97 deathsModerate damage ($1–5M)tsunami
- 1918M8.3
Mindanao: Cotabato
15 Aug 1918 · 252 km away · intensity X
52 deathsSevere damage ($5–24M)tsunami
- 1925M6.8
W. Luzon Island, Philippines
5 May 1925 · 209 km away · intensity IX
17 deathsModerate damage ($1–5M)tsunami
- 1897M8.7
Mindanao, Zamboanga, Sulu, Isabela
21 Sep 1897 · 285 km away · intensity IX
13 deathsSevere damage ($5–24M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.