All earthquakes
0.6
very light
EARTHQUAKE DETAILS

5 km South-East of Geraci Siculo

85 months ago · 15 Sept, 10:12

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

Stronger than 6% of Italian events in the past year

Where

5 km South-East of Geraci SiculoEarthquakes in the province of PalermoEarthquakes in Sicilia

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

16 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.1kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×3,981 its energy
M0this quakeM2

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 ≈ 23 s

Animation sped up ~4× compared to reality.

  • Caltanissetta
    42 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Bagheria
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Agrigento
    78 km from the epicentre
    first tremor in ~13 s
    main shaking in ~23 s
  • Gela
    80 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 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

18 km
medium depth
2 times the height of Mount Everest

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

in line with the area average (~19 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: 85 months ago the same area had a stronger quake (M2.6). This can only be said after the fact — it was not predictable beforehand.

2.6
The mainshock
6 km North-West of Gangi
85 months ago · 20 Sept, 21:31
Activity in the area right now (30 km radius)
0
last 24 hours
2
last 7 days
15
last 30 days
3 before12 after
this quake
Strongest of the sequence2.6

How often does it happen here?

about every ~6 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 697 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.

18235.8
Sicilia settentrionale earthquake
5 March 1823 · 43 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18195.4
Monti Madonie earthquake
24 February 1819 · 20 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18185.3
Monti Madonie earthquake
8 September 1818 · 11 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19675.3
Monti Nebrodi earthquake
31 October 1967 · 19 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.

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

The closest seismic structure

Gela-Catania

The epicentre lies about 55 km from Gela-Catania, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 3 and 10 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

1.1
85 months ago
12 Sept, 00:17
2.6
6 km North-West of Gangi
2 km South · 7 km
85 months ago
20 Sept, 21:31
1.7
84 months ago
21 Sept, 15:13
1.7
5 km South of Geraci Siculo
3 km South-West · 8 km
84 months ago
22 Sept, 04:49
1.6
84 months ago
22 Sept, 23:29
1.0
84 months ago
23 Sept, 11:18
2.3
5 km East of Petralia Soprana
3 km South-West · 8 km
84 months ago
26 Sept, 11:18
1.6
4 km East of Castelbuono
16 km North-West · 22 km
85 months ago
26 Aug, 15:04
1.6
5 km East of Petralia Soprana
3 km South-West · 10 km
84 months ago
5 Oct, 11:31
2.1
84 months ago
5 Oct, 12:50

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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