All earthquakes
1.7
very light
EARTHQUAKE DETAILS

9 km North-West of Nicolosi

91 months ago · 20 Dec, 01:16

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 78% of Italian events in the past year

Where

9 km North-West of NicolosiEarthquakes in the province of CataniaEarthquakes in Sicilia

Volcanic area: Mount Etna

Here the ground shakes mostly because of moving magma and underground fluids, not colliding plates: events are typically shallow, frequent and organised in swarms. This activity is constantly monitored by INGV.

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

61 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 ≈ 22 s

Animation sped up ~4× compared to reality.

  • Acireale
    20 km from the epicentre
    first tremor in ~4 s
    main shaking in ~6 s
  • Catania
    29 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Messina
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Reggio di Calabria
    77 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 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

8 km
shallow

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

in line with the area average (~13 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?

Seismic swarm

It is part of a seismic swarm: many closely spaced quakes in the same area, with no dominant shock. A typical, well-known behaviour of some Italian areas.

4.9
The mainshock
2 km North of Aci Sant'Antonio
91 months ago · 26 Dec, 03:19
Activity in the area right now (30 km radius)
26
last 24 hours
32
last 7 days
71
last 30 days
84 before599 after
this quake
Strongest of the sequence4.9

How often does it happen here?

about every ~2 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 2576 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.

18186.3
Catanese earthquake
20 February 1818 · 20 km from here
IX-XCompletely destructive: most buildings are destroyed.
17866.1
Golfo di Patti earthquake
10 March 1786 · 41 km from here
IXDestructive: many buildings partly or fully collapse.
16135.6
Monti Nebrodi earthquake
25 August 1613 · 46 km from here
IXDestructive: many buildings partly or fully collapse.
17805.5
Sicilia nord-orientale earthquake
28 March 1780 · 33 km from here
VII-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 15 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
8 km North of Ragalna
1 km West · 9 km
91 months ago
19 Dec, 23:12
1.6
91 months ago
19 Dec, 12:14
1.9
8 km South-East of Maletto
2 km North-West · 9 km
91 months ago
19 Dec, 06:08
1.7
7 km North of Ragalna
3 km South-West · 9 km
91 months ago
21 Dec, 02:07
2.5
9 km North of Ragalna
1 km West · 9 km
91 months ago
18 Dec, 10:31
1.8
8 km North of Ragalna
3 km West · 9 km
91 months ago
18 Dec, 10:31
1.9
91 months ago
18 Dec, 10:30
1.9
91 months ago
18 Dec, 06:07
2.0
5 km West of Sant'Alfio
5 km North-East · 10 km
91 months ago
17 Dec, 14:24
3.2
91 months ago
16 Dec, 20:29

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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