All earthquakes
1.8
very light
EARTHQUAKE DETAILS

5 km West of Troina

77 months ago · 23 Apr, 16:34

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

Stronger than 82% of Italian events in the past year

Where

5 km West of TroinaEarthquakes in the province of EnnaEarthquakes 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

61 events
Magnitude:lightweakmoderatestrong

The energy released

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

7.6kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×63 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 ≈ 23 s

Animation sped up ~4× compared to reality.

  • Catania
    49 km from the epicentre
    first tremor in ~9 s
    main shaking in ~16 s
  • Acireale
    51 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Caltanissetta
    62 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 s
  • Gela
    78 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

27 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 (~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?

Foreshock

In hindsight it was a foreshock: 77 months ago the same area had a stronger quake (M3.6). This can only be said after the fact — it was not predictable beforehand.

3.6
The mainshock
4 km West of Troina
77 months ago · 25 Apr, 09:21
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
8
last 30 days
28 before38 after
this quake
Strongest of the sequence3.6

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: 2370 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.

16135.6
Monti Nebrodi earthquake
25 August 1613 · 44 km from here
IXDestructive: many buildings partly or fully collapse.
17395.4
Monti Nebrodi earthquake
10 May 1739 · 40 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18185.3
Monti Madonie earthquake
8 September 1818 · 46 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19675.3
Monti Nebrodi earthquake
31 October 1967 · 20 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 32 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

2.7
6 km South-West of Troina
2 km South-West · 28 km
77 months ago
23 Apr, 16:06
2.1
2 km South-West of Troina
4 km East · 22 km
77 months ago
23 Apr, 15:29
2.7
4 km South-West of Troina
3 km South-East · 29 km
77 months ago
23 Apr, 15:16
2.0
5 km West of Troina
0 km North-West · 20 km
77 months ago
23 Apr, 14:25
1.5
77 months ago
23 Apr, 14:24
3.0
5 km West of Troina
1 km South-East · 24 km
77 months ago
23 Apr, 13:46
1.3
5 km West of Troina
0 km West · 25 km
77 months ago
23 Apr, 19:32
2.3
2 km South-West of Troina
4 km East · 31 km
77 months ago
23 Apr, 19:32
2.3
2 km South-West of Troina
4 km East · 32 km
77 months ago
23 Apr, 19:36
2.2
4 km South-West of Troina
3 km South-East · 30 km
77 months ago
23 Apr, 21:12

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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