All earthquakes
2.3
light
EARTHQUAKE DETAILS

M2.3 earthquake · 17 km North of Brolo (ME)

5 years ago · 25 Jul 2021, 07:37

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

Stronger than 93% of Italian events in the past year

Where

17 km North of BroloEarthquakes in the province of MessinaEarthquakes in Sicilia

Volcanic area: Aeolian Islands

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

23 events
Magnitude:lightweakmoderatestrong

The energy released

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

43kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×11 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 ≈ 48 s

Animation sped up ~9× compared to reality.

  • Messina
    63 km from the epicentre
    first tremor in ~25 s
    main shaking in ~43 s
  • Acireale
    81 km from the epicentre
    first tremor in ~27 s
    main shaking in ~45 s
  • Reggio di Calabria
    83 km from the epicentre
    first tremor in ~27 s
    main shaking in ~46 s
  • Catania
    94 km from the epicentre
    first tremor in ~28 s
    main shaking in ~48 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

137 km
deep
15 times the height of Mount Everest

Being deep, it is felt less at the surface.

deeper than the area average (~25 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: 5 years ago the same area had a stronger quake (M2.4). This can only be said after the fact — it was not predictable beforehand.

2.4
The mainshock
7 km North-West of Piraino
5 years ago · 9 Aug 2021, 03:04
Activity in the area right now (30 km radius)
0
last 24 hours
6
last 7 days
29
last 30 days
12 before10 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~3 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 1520 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 · 29 km from here
IXDestructive: many buildings partly or fully collapse.
19786.0
Golfo di Patti earthquake
15 April 1978 · 26 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18235.8
Sicilia settentrionale earthquake
5 March 1823 · 42 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16135.6
Monti Nebrodi earthquake
25 August 1613 · 20 km from here
IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Milazzo-Eolie

The epicentre lies about 11 km from Milazzo-Eolie, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.9between 1 and 25 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

2.3
5 years ago
25 Jul 2021, 06:17
0.9
9 km North of Piraino
9 km South-East · 9 km
5 years ago
23 Jul 2021, 00:25
0.9
5 years ago
22 Jul 2021, 03:15
0.7
5 years ago
29 Jul 2021, 03:24
1.3
2 km North of Oliveri
28 km South-East · 8 km
5 years ago
12 Jul 2021, 13:56
2.3
14 km North of Gioiosa Marea
12 km East · 133 km
5 years ago
12 Jul 2021, 04:23
0.9
7 km North-West of Terme Vigliatore
29 km South-East · 10 km
5 years ago
8 Aug 2021, 07:05
1.0
2 km South-West of Gioiosa Marea
20 km South-East · 17 km
5 years ago
8 Aug 2021, 09:05
2.4
7 km North-West of Piraino
11 km South-East · 123 km
5 years ago
9 Aug 2021, 03:04
1.3
4 km East of Sinagra
26 km South · 22 km
5 years ago
10 Aug 2021, 02:08

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).