All earthquakes
1.7
very light
EARTHQUAKE DETAILS

1 km East of Calascibetta

134 months ago · 4 Sept, 10:57

A very light earthquake, probably not felt by people. At only a few km deep the shaking is felt more sharply at the surface.

Stronger than 78% of Italian events in the past year

Where

1 km East of CalascibettaEarthquakes 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

27 events
Magnitude:lightweakmoderatestrong

The energy released

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

5.4kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×89 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 ≈ 21 s

Animation sped up ~4× compared to reality.

  • Caltanissetta
    28 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Gela
    59 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Agrigento
    68 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Catania
    72 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 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

9 km
shallow
1 times the height of Mount Everest

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

shallower than the area average (~20 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 (M2.6, 135 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.6
The mainshock
4 km North of Villarosa
135 months ago · 5 Aug, 21:47
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
3
last 30 days
22 before4 after
this quake
Strongest of the sequence2.6

How often does it happen here?

about every ~6 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 679 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.

18195.4
Monti Madonie earthquake
24 February 1819 · 38 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18185.3
Monti Madonie earthquake
8 September 1818 · 25 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19675.3
Monti Nebrodi earthquake
31 October 1967 · 29 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
17185.3
Sicilia orientale earthquake
20 February 1718 · 33 km from here
VI-VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.

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

The closest seismic structure

Gela-Catania

The epicentre lies about 36 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

1.0
134 months ago
6 Sept, 18:57
1.5
134 months ago
27 Aug, 14:32
2.0
134 months ago
27 Aug, 13:40
1.7
134 months ago
27 Aug, 13:31
1.2
3 km South-West of Petralia Soprana
20 km North-West · 35 km
134 months ago
27 Aug, 02:09
0.9
133 months ago
16 Sept, 01:51
2.0
5 km South of Leonforte
10 km East · 36 km
134 months ago
14 Aug, 20:16
1.0
3 km North of Petralia Soprana
22 km North-West · 8 km
134 months ago
14 Aug, 05:33
2.1
6 km South of Leonforte
12 km East · 60 km
135 months ago
9 Aug, 16:05
1.8
5 km West of Calascibetta
7 km West · 11 km
135 months ago
6 Aug, 06:37

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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