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EARTHQUAKE DETAILS

M2.5 offshore earthquake

5 years ago · 15 Jul 2021, 18:00

A light earthquake, rarely felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 95% of Italian events in the past year

Where

Nearest Italian town: Leni (ME)Earthquakes in the province of MessinaEarthquakes in Sicilia

Epicentre at sea

The epicentre is at sea: for the same magnitude, the shaking is felt less on land, because the energy fades along the way before reaching the coast.

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

11 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 ≈ 36 s

Animation sped up ~7× compared to reality.

  • Bagheria
    101 km from the epicentre
    first tremor in ~17 s
    main shaking in ~29 s
  • Messina
    103 km from the epicentre
    first tremor in ~17 s
    main shaking in ~30 s
  • Palermo
    111 km from the epicentre
    first tremor in ~19 s
    main shaking in ~32 s
  • Reggio di Calabria
    123 km from the epicentre
    first tremor in ~21 s
    main shaking in ~36 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

18 km
medium depth
2 times the height of Mount Everest

At this depth the shaking is felt, but rarely causes damage.

shallower than the area average (~36 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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by one aftershock within 30 km. Aftershocks tend to fade in number and strength over time.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
10
last 30 days
9 before1 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~12 days

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 362 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.

18235.8
Sicilia settentrionale earthquake
5 March 1823 · 46 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
19805.7
Tirreno meridionale earthquake
28 May 1980 · 20 km from here
VI-VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
20045.4
Isole Eolie earthquake
5 May 2004 · 30 km from here
IVModerate: felt by many indoors; glasses and dishes rattle.
19575.3
Tirreno meridionale earthquake
21 May 1957 · 29 km from here
IV-VRather strong: felt by almost everyone; hanging objects swing.

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

The closest seismic structure

Southern Tyrrhenian

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

estimated maximum magnitude 8.2between 2 and 18 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

1.9
Isole Eolie (Messina)
14 km South-West · 8 km
5 years ago
12 Jul 2021, 23:53
1.4
Isole Eolie (Messina)
15 km South-West · 7 km
5 years ago
12 Jul 2021, 23:25
2.4
Isole Eolie (Messina)
13 km West · 10 km
5 years ago
12 Jul 2021, 23:05
1.4
Isole Eolie (Messina)
16 km West · 10 km
5 years ago
6 Jul 2021, 04:02
1.7
Isole Eolie (Messina)
14 km West · 7 km
5 years ago
5 Jul 2021, 03:47
1.7
Isole Eolie (Messina)
4 km South · 9 km
5 years ago
3 Jul 2021, 14:10
1.3
Costa Siciliana nord-orientale (Messina)
29 km South-East · 9 km
5 years ago
1 Jul 2021, 17:52
2.2
Tirreno Meridionale [Mare]
22 km West · 10 km
5 years ago
1 Aug 2021, 23:05
2.3
Costa Siciliana nord-orientale (Messina)
28 km South-East · 9 km
5 years ago
22 Jun 2021, 09:05
1.5
Costa Siciliana nord-orientale (Messina)
28 km South-East · 10 km
5 years ago
15 Jun 2021, 21:27

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).