All earthquakes
1.5
very light
EARTHQUAKE DETAILS

3 km West of Valgrana

26 months ago · 22 Jul, 10:40

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 68% of Italian events in the past year

Where

3 km West of ValgranaEarthquakes in the province of CuneoEarthquakes 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

30 events
Magnitude:lightweakmoderatestrong

The energy released

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

2.7kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×178 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 ≈ 24 s

Animation sped up ~4× compared to reality.

  • Cuneo
    17 km from the epicentre
    first tremor in ~3 s
    main shaking in ~5 s
  • Moncalieri
    70 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Sanremo
    72 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 s
  • Torino
    83 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 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

6 km
shallow

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

in line with the area average (~11 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: 25 months ago the same area had a stronger quake (M1.9). This can only be said after the fact — it was not predictable beforehand.

1.9
The mainshock
2 km North of Castelmagno
25 months ago · 5 Aug, 09:23
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
8
last 30 days
20 before9 after
this quake
Strongest of the sequence1.9

How often does it happen here?

about every ~17 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 248 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.

15645.8
Lantosque earthquake
20 July 1564 · 42 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 47 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18085.6
Val Pellice earthquake
2 April 1808 · 49 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 49 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.

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

The closest seismic structure

Southern Piemonte

The epicentre lies about 29 km from Southern Piemonte, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.3between 2 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

1.2
26 months ago
22 Jul, 09:55
0.7
26 months ago
20 Jul, 17:37
1.4
26 months ago
20 Jul, 16:24
1.3
3 km West of Valgrana
1 km North-West · 7 km
26 months ago
20 Jul, 15:32
1.5
1 km North of Monterosso Grana
3 km South-West · 8 km
25 months ago
24 Jul, 17:58
0.8
25 months ago
24 Jul, 18:04
1.5
3 km North-East of Demonte
7 km South-West · 13 km
26 months ago
17 Jul, 07:25
1.5
5 km North-East of Sampeyre
26 km North-West · 11 km
26 months ago
14 Jul, 10:00
1.3
0 km East of Monterosso Grana
3 km South-West · 8 km
26 months ago
12 Jul, 17:59
1.3
3 km South of Cartignano
8 km North-West · 11 km
25 months ago
1 Aug, 21:44

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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