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2.5
light
EARTHQUAKE DETAILS

6 km East of Acireale

87 months ago · 22 Jul, 13:46

A light earthquake, rarely felt by people. At only a few km deep the shaking is felt more sharply at the surface.

Stronger than 96% of Italian events in the past year

Where

6 km East of AcirealeEarthquakes in the province of CataniaEarthquakes 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

31 events
Magnitude:lightweakmoderatestrong

The energy released

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

85kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×5.6 its energy
M2this quakeM4

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 ≈ 20 s

Animation sped up ~4× compared to reality.

  • Acireale
    6 km from the epicentre
    first tremor in ~2 s
    main shaking in ~3 s
  • Catania
    24 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Messina
    68 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 s
  • Reggio di Calabria
    68 km from the epicentre
    first tremor in ~11 s
    main shaking in ~20 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

6 km
shallow

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

shallower 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: 86 months ago the same area had a stronger quake (M2.9). This can only be said after the fact — it was not predictable beforehand.

2.9
The mainshock
2 km East of Santa Venerina
86 months ago · 21 Aug, 13:44
Activity in the area right now (30 km radius)
0
last 24 hours
2
last 7 days
17
last 30 days
10 before20 after
this quake
Strongest of the sequence2.9

How often does it happen here?

about every ~7 days

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 576 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.

18186.3
Catanese earthquake
20 February 1818 · 9 km from here
IX-XCompletely destructive: most buildings are destroyed.
19905.6
Sicilia sud-orientale earthquake
13 December 1990 · 40 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
17805.5
Sicilia nord-orientale earthquake
28 March 1780 · 28 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18485.5
Golfo di Catania earthquake
11 January 1848 · 22 km from here
VIII-IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Gela-Catania

The epicentre sits above this source area: the deep structure where this area's earthquakes can originate.

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

1.7
8 km East of Acireale
2 km East · 7 km
87 months ago
22 Jul, 14:21
1.4
87 months ago
20 Jul, 11:57
2.7
1 km North of Milo
18 km North-West · 9 km
87 months ago
25 Jul, 15:47
1.6
3 km South-West of Sant'Alfio
19 km North-West · 8 km
87 months ago
15 Jul, 04:58
2.2
1 km South of Sant'Alfio
20 km North-West · 7 km
86 months ago
30 Jul, 18:56
2.4
2 km North of Giarre
13 km North-West · 5 km
87 months ago
12 Jul, 12:21
1.8
2 km North-East of Milo
16 km North-West · 8 km
86 months ago
3 Aug, 09:56
1.1
17 km North-East of Augusta
30 km South · 24 km
86 months ago
3 Aug, 10:01
1.9
1 km North of Mascali
16 km North-West · 7 km
86 months ago
5 Aug, 23:05
1.6
7 km East of Maletto
29 km North-West · 26 km
86 months ago
6 Aug, 00:11

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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