All earthquakes
0.5
very light
EARTHQUAKE DETAILS

1 km North of Perosa Argentina

122 months ago · 1 Sept, 03:03

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 3% of Italian events in the past year

Where

1 km North of Perosa ArgentinaEarthquakes in the province of TorinoEarthquakes in Piemonte

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

9 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.1kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×5,623 its energy
M0this quakeM2

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 ≈ 23 s

Animation sped up ~4× compared to reality.

  • Moncalieri
    41 km from the epicentre
    first tremor in ~7 s
    main shaking in ~12 s
  • Torino
    43 km from the epicentre
    first tremor in ~7 s
    main shaking in ~13 s
  • Cuneo
    70 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Asti
    81 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 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.

in line with the area average (~12 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: 121 months ago the same area had a stronger quake (M1.3). This can only be said after the fact — it was not predictable beforehand.

1.3
The mainshock
2 km North of Chiusa di San Michele
121 months ago · 23 Sept, 15:15
Activity in the area right now (30 km radius)
0
last 24 hours
2
last 7 days
6
last 30 days
3 before5 after
this quake
Strongest of the sequence1.3

How often does it happen here?

about every ~33 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 130 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.

18085.6
Val Pellice earthquake
2 April 1808 · 17 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18085.3
Val Pellice earthquake
16 April 1808 · 19 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19145.2
Torinese earthquake
26 October 1914 · 15 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
18865.2
Torinese earthquake
5 September 1886 · 11 km from here
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

Western Piemonte

The epicentre lies about 14 km from Western Piemonte, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 1 and 8 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

0.7
2 km West of Inverso Pinasca
6 km South · 11 km
121 months ago
7 Sept, 02:31
1.1
2 km South-East of Rorà
25 km South · 12 km
121 months ago
10 Sept, 12:27
0.9
1 km South-West of Giaveno
9 km East · 13 km
121 months ago
12 Sept, 05:18
0.8
1 km East of Villar Focchiardo
11 km North · 10 km
122 months ago
15 Aug, 08:36
1.2
2 km East of Coazze
10 km North-East · 10 km
122 months ago
15 Aug, 08:36
1.3
2 km North of Chiusa di San Michele
17 km North-East · 10 km
121 months ago
23 Sept, 15:15
1.3
3 km East of Rorà
23 km South · 12 km
122 months ago
4 Aug, 08:20
0.8
1 km North-East of Pinasca
5 km East · 13 km
121 months ago
30 Sept, 00:57

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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