All earthquakes
1.5
very light
EARTHQUAKE DETAILS

7 km East of Courmayeur

84 months ago · 29 Sept, 15:17

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

7 km East of CourmayeurEarthquakes in the province of AostaEarthquakes in Valle d'Aosta

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

61 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 ≈ 40 s

Animation sped up ~7× compared to reality.

  • Torino
    98 km from the epicentre
    first tremor in ~16 s
    main shaking in ~28 s
  • Moncalieri
    110 km from the epicentre
    first tremor in ~18 s
    main shaking in ~32 s
  • Novara
    131 km from the epicentre
    first tremor in ~22 s
    main shaking in ~38 s
  • Asti
    138 km from the epicentre
    first tremor in ~23 s
    main shaking in ~40 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

10 km
shallow
1.1 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 (~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 (M1.8, 84 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

1.8
The mainshock
9 km West of Saint-Rhémy-en-Bosses
84 months ago · 28 Sept, 18:36
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
15 before61 after
this quake
Strongest of the sequence1.8

How often does it happen here?

about every ~44 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 97 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.

18175.4
Massif du Mont-Blanc earthquake
11 March 1817 · 29 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
18795.2
Chablais earthquake
30 December 1879 · 42 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19055.1
Haute-Savoie, Vallorcine earthquake
29 April 1905 · 20 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19054.9
Massif du Mont-Blanc earthquake
13 August 1905 · 15 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

Chamonix

The epicentre lies about 9 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

1.7
8 km East of Courmayeur
2 km North-East · 10 km
84 months ago
29 Sept, 15:00
1.0
84 months ago
29 Sept, 08:40
0.9
84 months ago
29 Sept, 03:30
1.0
84 months ago
29 Sept, 03:29
1.8
9 km West of Saint-Rhémy-en-Bosses
4 km North-East · 11 km
84 months ago
28 Sept, 18:36
1.2
84 months ago
26 Sept, 08:09
0.9
84 months ago
7 Oct, 01:20
1.5
84 months ago
7 Oct, 01:37
1.7
4 km North-East of Courmayeur
5 km North-West · 10 km
84 months ago
7 Oct, 15:57
1.3
84 months ago
20 Sept, 00:47

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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