All earthquakes
1.2
very light
EARTHQUAKE DETAILS

M1.2 earthquake outside Italy

6 years ago · 4 Sept 2020, 11:13

A very light earthquake, probably not felt by people. At this depth the shaking is felt, but rarely causes damage.

Where

Nearest Italian town: Valgrisenche (AO)Earthquakes in the province of AostaEarthquakes in Valle d'Aosta

Epicentre abroad

The epicentre lies outside Italy's borders. The quake appears here because the INGV seismic network also records events close to Italy, which can be felt on Italian territory.

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.

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 ≈ 38 s

Animation sped up ~7× compared to reality.

  • Torino
    85 km from the epicentre
    first tremor in ~14 s
    main shaking in ~25 s
  • Moncalieri
    92 km from the epicentre
    first tremor in ~16 s
    main shaking in ~27 s
  • Asti
    129 km from the epicentre
    first tremor in ~22 s
    main shaking in ~37 s
  • Cuneo
    133 km from the epicentre
    first tremor in ~22 s
    main shaking in ~38 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

11 km
medium depth
1.3 times the height of Mount Everest

At this depth the shaking is felt, but rarely causes damage.

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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.7, 6 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.7
The mainshock
10 km West of Balme
6 years ago · 6 Aug 2020, 20:28
Activity in the area right now (30 km radius)
0
last 24 hours
4
last 7 days
9
last 30 days
5 before3 after
this quake
Strongest of the sequence2.7

How often does it happen here?

about every ~45 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 95 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.

19804.8
Bauges earthquake
2 December 1980 · 38 km from here
VI-VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
18494.7
Maurienne earthquake
1 October 1849 · 42 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18394.6
Maurienne earthquake
26 March 1839 · 44 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18814.6
Belledonne-Pelvoux earthquake
22 July 1881 · 38 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

Chamonix

The epicentre lies about 36 km from Chamonix, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.0between 3 and 15 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

1.3
25 km North-West of Moncenisio
18 km South · 14 km
6 years ago
21 Aug 2020, 23:41
1.7
24 km North-West of Moncenisio
18 km South · 12 km
6 years ago
20 Aug 2020, 23:15
1.1
5 km South-East of La Thuile
28 km North-East · 8 km
6 years ago
19 Sept 2020, 13:50
0.6
9 km West of Valgrisenche
18 km North-East · 10 km
6 years ago
23 Sept 2020, 10:02
0.3
4 km South-West of La Thuile
24 km North-East · 7 km
6 years ago
16 Aug 2020, 03:39
1.0
3 km South-East of La Thuile
28 km North-East · 8 km
6 years ago
16 Aug 2020, 03:13
2.3
3 km North-West of Valgrisenche
25 km North-East · 10 km
6 years ago
1 Oct 2020, 10:25
2.7
10 km West of Balme
29 km South-East · 11 km
6 years ago
6 Aug 2020, 20:28

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).