All earthquakes
0.9
very light
EARTHQUAKE DETAILS

3 km South-West of Roaschia

101 months ago · 6 May, 20:20

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 23% of Italian events in the past year

Where

3 km South-West of RoaschiaEarthquakes 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

10 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.3kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×1,413 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 ≈ 25 s

Animation sped up ~5× compared to reality.

  • Cuneo
    22 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Sanremo
    51 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Savona
    82 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 s
  • Moncalieri
    85 km from the epicentre
    first tremor in ~14 s
    main shaking in ~25 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 (~10 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: 100 months ago the same area had a stronger quake (M2.2). This can only be said after the fact — it was not predictable beforehand.

2.2
The mainshock
2 km North of Gaiola
100 months ago · 28 May, 14:44
Activity in the area right now (30 km radius)
1
last 24 hours
3
last 7 days
7
last 30 days
4 before5 after
this quake
Strongest of the sequence2.2

How often does it happen here?

about every ~27 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 155 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 · 26 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 33 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 31 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19194.9
Alpi Marittime earthquake
28 November 1919 · 26 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.

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

The closest seismic structure

Southern Piemonte

The epicentre lies about 43 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

1.1
4 km South-West of Limone Piemonte
10 km South-East · 8 km
101 months ago
9 May, 08:50
1.0
101 months ago
10 May, 04:27
2.0
10 km South-West of Valdieri
18 km West · 11 km
101 months ago
30 Apr, 20:41
1.0
2 km North-East of Roaschia
5 km North-East · 6 km
101 months ago
14 May, 12:46
0.8
6 km South-West of Valdieri
14 km West · 10 km
102 months ago
23 Apr, 18:13
1.2
1 km West of Monterosso Grana
21 km North-West · 10 km
102 months ago
22 Apr, 13:54
1.6
5 km North-West of Roaschia
6 km North-West · 11 km
102 months ago
19 Apr, 09:12
1.4
1 km West of Vernante
6 km East · 8 km
101 months ago
27 May, 21:43
2.2
2 km North of Gaiola
14 km North · 11 km
100 months ago
28 May, 14:44

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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