All earthquakes
1.7
very light
EARTHQUAKE DETAILS

4 km West of San Marco la Catola

110 months ago · 12 Aug, 23:21

A very light earthquake, probably not felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 78% of Italian events in the past year

Where

4 km West of San Marco la CatolaEarthquakes in the province of FoggiaEarthquakes in Puglia

How far away could it be felt?

A quake this small is usually not felt by people: only seismographs record it.

Statistical estimate from the Italian intensity attenuation model (INGV): actual perception depends on geology, buildings and depth. Very shallow events can be felt locally even below the threshold.

Earthquake map

24 events
Magnitude:lightweakmoderatestrong

The energy released

How much energy this quake unleashed, translated into everyday comparisons.

5.4kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×89 its energy
M1this quakeM3

Each extra magnitude unit releases about 32 times more energy: an M5 is not "a bit stronger" than an M4 — it is a different league.

Energy estimated with the standard Gutenberg–Richter relation; an average lightning bolt ≈ 1 billion joules. Indicative values.

The race of the seismic waves

Two waves set off from the hypocentre: the faster P wave arrives first with a sharp jolt; the S wave carries the actual shaking.

P waves — the first sharp jolt (~6 km/s)S waves — the strongest shaking (~3.5 km/s)
t ≈ 21 s

Animation sped up ~4× compared to reality.

  • Benevento
    43 km from the epicentre
    first tremor in ~8 s
    main shaking in ~14 s
  • San Severo
    44 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Foggia
    53 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Avellino
    67 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 s

Theoretical times with average crustal speeds: real values vary with geology. The gap between P and S waves is what earthquake early-warning systems rely on.

How deep it was born

26 km
medium depth
3 times the height of Mount Everest

At this depth the shaking is felt, but rarely causes damage.

deeper than the area average (~15 km)

For the same magnitude, a shallow earthquake is felt much more than a deep one: the energy starts closer to the surface.

What kind of quake is this?

Foreshock

In hindsight it was a foreshock: 110 months ago the same area had a stronger quake (M2.0). This can only be said after the fact — it was not predictable beforehand.

2.0
The mainshock
2 km North-West of Sant'Elia a Pianisi
110 months ago · 30 Aug, 10:18
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
6
last 30 days
9 before14 after
this quake
Strongest of the sequence2.0

How often does it happen here?

about every ~8 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 530 events in the last 12 years of the INGV catalogue.

An average computed on the recent past: it tells how used this area is to shaking, not when the next quake will come — earthquakes cannot be predicted.

The great earthquakes in this area's history

Almost a thousand years of catalogues: the strongest documented events within ~50 km.

14567.2
Appennino centro-meridionale earthquake
5 December 1456 · 32 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
16887.1
Sannio earthquake
5 June 1688 · 43 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
17326.8
Irpinia earthquake
29 November 1732 · 50 km from here
X-XICatastrophic: very few buildings remain standing; landslides and ground cracks.
18056.7
Molise earthquake
26 July 1805 · 42 km from here
XCompletely destructive: most buildings are destroyed.

Source: Parametric Catalogue of Italian Earthquakes CPTI15 (INGV, CC BY 4.0).

The closest seismic structure

Ripabottoni-San Severo

The epicentre lies about 19 km from Ripabottoni-San Severo, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 6 and 25 km deep

Faults are mapped to build better and understand the territory: knowing them says nothing about when an earthquake will occur, which remains unpredictable. Source: DISS 3.3 (INGV, CC BY 4.0).

Other quakes in the area

1.9
110 months ago
12 Aug, 09:18
0.7
3 km South-East of Provvidenti
25 km North-West · 15 km
110 months ago
8 Aug, 21:49
1.0
110 months ago
19 Aug, 20:14
1.2
110 months ago
19 Aug, 20:47
1.1
4 km West of San Marco la Catola
1 km North-West · 20 km
110 months ago
19 Aug, 20:51
1.3
110 months ago
20 Aug, 05:06
1.4
3 km West of Cercemaggiore
23 km West · 12 km
110 months ago
4 Aug, 01:47
1.5
110 months ago
23 Aug, 02:33
1.8
5 km East of Campobasso
25 km West · 24 km
110 months ago
26 Aug, 23:37
1.1
110 months ago
27 Aug, 01:50

Data: INGV — National Institute of Geophysics and Volcanology (CC-BY 4.0)

Estimates computed by Meteare on INGV data (Gutenberg–Richter relation; Italian macroseismic intensity attenuation model).

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