All earthquakes
1.2
very light
EARTHQUAKE DETAILS

6 km East of Geraci Siculo

107 months ago · 18 Aug, 08:49

A very light earthquake, probably not felt by people. At only a few km deep the shaking is felt more sharply at the surface.

Stronger than 47% of Italian events in the past year

Where

6 km 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

8 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.0kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×501 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 ≈ 24 s

Animation sped up ~4× compared to reality.

  • Caltanissetta
    46 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Bagheria
    70 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Catania
    81 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 s
  • Gela
    83 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 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

9 km
shallow

At only a few km deep the shaking is felt more sharply at the surface.

shallower than the area average (~18 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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.4, 108 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.4
The mainshock
4 km South-West of Polizzi Generosa
108 months ago · 28 Jul, 11:35
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
3
last 30 days
4 before3 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~5 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 763 events in the last 11 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 · 39 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18195.4
Monti Madonie earthquake
24 February 1819 · 21 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18185.3
Monti Madonie earthquake
8 September 1818 · 15 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19675.3
Monti Nebrodi earthquake
31 October 1967 · 15 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 56 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

1.3
107 months ago
18 Aug, 09:37
1.8
107 months ago
16 Aug, 16:28
1.1
7 km West of Geraci Siculo
14 km West · 8 km
107 months ago
28 Aug, 09:17
1.6
10 km North of Caronia
30 km North-East · 11 km
108 months ago
8 Aug, 05:12
1.3
3 km South-West of Capizzi
19 km East · 10 km
107 months ago
8 Sept, 04:34
2.4
108 months ago
28 Jul, 11:35
2.1
1 km West of Mistretta
11 km East · 5 km
108 months ago
28 Jul, 07:40

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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