All earthquakes
2.1
light
EARTHQUAKE DETAILS

2 km South-West of Valgrana

60 months ago · 13 Sept, 16:23

A light earthquake, rarely felt by people. At only a few km deep the shaking is felt more sharply at the surface.

Stronger than 90% of Italian events in the past year

Where

2 km South-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

18 events
Magnitude:lightweakmoderatestrong

The energy released

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

21kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×22 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 ~5× compared to reality.

  • Cuneo
    16 km from the epicentre
    first tremor in ~3 s
    main shaking in ~5 s
  • Sanremo
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Moncalieri
    72 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 s
  • Torino
    85 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

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 (~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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by 6 aftershocks within 30 km. Aftershocks tend to fade in number and strength over time.

Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
10
last 30 days
11 before6 after
this quake
Strongest of the sequence1.6

How often does it happen here?

about every ~18 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 236 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 · 40 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 46 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 47 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19595.4
Ubaye earthquake
5 April 1959 · 49 km from here
VII-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 30 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

1.5
2 km North-West of Rittana
1 km South-West · 10 km
60 months ago
13 Sept, 14:12
1.4
1 km North-West of Pradleves
9 km North-West · 14 km
60 months ago
16 Sept, 14:27
1.1
3 km North-East of Demonte
8 km West · 10 km
60 months ago
16 Sept, 21:16
0.7
3 km West of Valloriate
4 km South-West · 8 km
60 months ago
10 Sept, 01:01
0.7
3 km West of Valloriate
4 km South-West · 9 km
61 months ago
5 Sept, 06:41
0.9
3 km North of Boves
18 km East · 10 km
60 months ago
22 Sept, 17:20
1.1
4 km South-West of Prazzo
27 km West · 14 km
61 months ago
4 Sept, 10:37
0.9
5 km East of Vinadio
21 km South-West · 11 km
61 months ago
2 Sept, 21:39
1.3
2 km West of Valgrana
2 km North-West · 9 km
61 months ago
2 Sept, 18:28
1.6
4 km South of Prazzo
26 km West · 10 km
61 months ago
31 Aug, 16:07

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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