All earthquakes
1.2
very light
EARTHQUAKE DETAILS

M1.2 earthquake · 3 km North of Cervasca (CN)

5 years ago · 4 May 2021, 01:37

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 48% of Italian events in the past year

Where

3 km North of CervascaEarthquakes 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

7 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.0kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×501 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.

  • Cuneo
    5 km from the epicentre
    first tremor in ~2 s
    main shaking in ~3 s
  • Moncalieri
    65 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 s
  • Sanremo
    68 km from the epicentre
    first tremor in ~11 s
    main shaking in ~20 s
  • Torino
    78 km from the epicentre
    first tremor in ~13 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

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: 5 years ago the same area had a stronger quake (M2.5). This can only be said after the fact — it was not predictable beforehand.

2.5
The mainshock
2 km North of San Damiano Macra
5 years ago · 7 May 2021, 17:05
Activity in the area right now (30 km radius)
0
last 24 hours
6
last 7 days
20
last 30 days
2 before4 after
this quake
Strongest of the sequence2.5

How often does it happen here?

about every ~22 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 197 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 · 46 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18085.0
Val Pellice earthquake
2 April 1808 · 49 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19194.9
Alpi Marittime earthquake
28 November 1919 · 34 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18784.9
Cuneese earthquake
7 June 1878 · 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

Southern Piemonte

The epicentre lies about 22 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

1.7
3 km North of Pradleves
17 km West · 12 km
5 years ago
6 May 2021, 23:27
2.5
5 years ago
7 May 2021, 17:05
1.4
5 years ago
27 Apr 2021, 05:33
1.6
1 km North-West of Macra
27 km West · 10 km
5 years ago
13 May 2021, 23:52
1.1
1 km West of Pradleves
19 km West · 11 km
5 years ago
20 May 2021, 02:22
1.9
2 km East of Celle di Macra
24 km West · 13 km
5 years ago
13 Apr 2021, 00:14

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).