All earthquakes
2.0
light
EARTHQUAKE DETAILS

3 km South of San Marco d'Alunzio

96 months ago · 31 Jul, 05:22

A light earthquake, rarely felt by people. Being deep, it is felt less at the surface.

Stronger than 88% of Italian events in the past year

Where

3 km South of San Marco d'AlunzioEarthquakes in the province of MessinaEarthquakes 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.

15kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×32 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 ≈ 28 s

Animation sped up ~5× compared to reality.

  • Acireale
    60 km from the epicentre
    first tremor in ~13 s
    main shaking in ~21 s
  • Catania
    69 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 s
  • Messina
    73 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 s
  • Caltanissetta
    88 km from the epicentre
    first tremor in ~16 s
    main shaking in ~28 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

44 km
deep
5 times the height of Mount Everest

Being deep, it is felt less at the surface.

deeper than the area average (~14 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 (M2.2, 96 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.2
The mainshock
1 km North-West of Troina
96 months ago · 26 Jul, 21:33
Activity in the area right now (30 km radius)
11
last 24 hours
16
last 7 days
53
last 30 days
8 before7 after
this quake
Strongest of the sequence2.2

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: 2575 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.

17866.1
Golfo di Patti earthquake
10 March 1786 · 28 km from here
IXDestructive: many buildings partly or fully collapse.
18235.8
Sicilia settentrionale earthquake
5 March 1823 · 36 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16135.6
Monti Nebrodi earthquake
25 August 1613 · 12 km from here
IXDestructive: many buildings partly or fully collapse.
17395.4
Monti Nebrodi earthquake
10 May 1739 · 8 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

Patti-Giardini

The epicentre lies about 35 km from Patti-Giardini, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 3 and 20 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

1.8
4 km West of Galati Mamertino
6 km South-East · 46 km
96 months ago
31 Jul, 05:37
1.9
4 km South of San Marco d'Alunzio
2 km South-East · 42 km
96 months ago
31 Jul, 04:51
2.1
9 km North-West of Piraino
24 km North-East · 133 km
96 months ago
29 Jul, 23:43
2.2
1 km North-West of Troina
29 km South · 31 km
96 months ago
26 Jul, 21:33
1.1
2 km East of Randazzo
29 km South-East · 11 km
96 months ago
4 Aug, 20:56
1.7
4 km East of Bronte
25 km South-East · 30 km
96 months ago
6 Aug, 15:22
1.9
2 km West of Gioiosa Marea
22 km North-East · 12 km
96 months ago
21 Jul, 23:56
0.8
3 km West of Basicò
29 km East · 11 km
96 months ago
10 Aug, 02:56
1.5
3 km East of Floresta
22 km East · 29 km
95 months ago
15 Aug, 05:22
1.3
3 km East of San Piero Patti
26 km East · 39 km
95 months ago
18 Aug, 13:34

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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