QuakeScout
Magnitude6.5

Reviewed by USGSIndonesia52y ago

M6.5 earthquake 260 km SSW of Kroya, Indonesia

Saturday, September 7, 1974, 20:43:11 UTC · 9.815°S, 108.356°E

A magnitude 6.5 earthquake struck 260 km SSW of Kroya, Indonesia on Saturday, September 7, 1974, 20:43:11 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.4 on July 23, 1943.

Magnitude
6.5
Strong · ms
Depth
33 km
Shallow
Felt reports
0
Did You Feel It?
Est. shaking
—
No ShakeMap
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeDashed circle: 100 km aftershock search area

In context

How big was it, and why here?

Energy released

85 kilotons of TNT

That is about 6 times the Hiroshima bomb. It released about 178 times the energy of a magnitude 5.0.

Tectonic setting

39 km

from the nearest mapped plate boundary, between the Sunda and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

33 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 100 km

USGS lists 2 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M4.7 on September 12, 1974. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M5M61h6h1d3d7d14d30dMainshock M6.5
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.5260 km SSW of Sidareja, Indonesia52y ago · 20 km W of this epicenter
  2. 4.7254 km SSW of Kroya, Indonesia52y ago · 20 km E of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 35 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.6233 km S of Pundong, IndonesiaSeptember 11, 1921 · 253 km E of this epicenter
  2. 7.487 km SSW of Srandakan, IndonesiaJuly 23, 1943 · 210 km NE of this epicenter
  3. 7.1138 km SSE of Pundong, IndonesiaSeptember 10, 1926 · 260 km E of this epicenter
  4. 6.992 km S of Pundong, IndonesiaSeptember 27, 1937 · 254 km NE of this epicenter
  5. 6.4244 km SSW of Trenggalek, IndonesiaMay 29, 1955 · 287 km E of this epicenter
  6. 6.3136 km S of Kawalu, IndonesiaSeptember 14, 1944 · 138 km N of this epicenter
  7. 6.3south of Java, IndonesiaMarch 21, 1940 · 84 km SW of this epicenter
  8. 6.2166 km SSW of Bambanglipuro, IndonesiaAugust 31, 1918 · 173 km E of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 214 recorded deaths. The most severe:

  1. 1943M8.1

    Java: Jogyakarta

    23 Jul 1943 · 184 km away · intensity VIII

    213 deathsSevere damage ($5–24M)

  2. 1937M7.2

    Java: Jogyakarta: Klumpit,Prambanan

    27 Sep 1937 · 207 km away · intensity IX

    1 deathSevere damage ($5–24M)

  3. 1863

    Java: Banyumas

    31 Jul 1863 · 278 km away

    Moderate damage ($1–5M)

  4. 1923

    Java: Maos

    15 May 1923 · 253 km away · intensity IX

    Moderate damage ($1–5M)

  5. 1904

    S. Java

    7 Sep 1904 · 246 km away

    tsunami

  6. 1957

    S. Java Sea

    26 Sep 1957 · 214 km away

    tsunami

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

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