All earthquakes
1.3
very light
EARTHQUAKE DETAILS

M1.3 earthquake · 4 km West of Acceglio (CN)

11 years ago · 9 Jul 2015, 20:38

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 55% of Italian events in the past year

Where

4 km West of AcceglioEarthquakes 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

46 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×355 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 ≈ 29 s

Animation sped up ~5× compared to reality.

  • Cuneo
    51 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Moncalieri
    82 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 s
  • Torino
    92 km from the epicentre
    first tremor in ~15 s
    main shaking in ~26 s
  • Sanremo
    100 km from the epicentre
    first tremor in ~17 s
    main shaking in ~29 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
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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.8, 11 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.8
The mainshock
5 km South of Paesana
11 years ago · 18 Jun 2015, 00:04
Activity in the area right now (30 km radius)
0
last 24 hours
5
last 7 days
20
last 30 days
29 before16 after
this quake
Strongest of the sequence2.8

How often does it happen here?

about every ~15 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 283 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.

18085.6
Val Pellice earthquake
2 April 1808 · 47 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19595.4
Ubaye earthquake
5 April 1959 · 13 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19355.3
Embrunais earthquake
19 March 1935 · 30 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18085.1
Val Pellice earthquake
18 April 1808 · 48 km from here
VI-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

Brianconnais

The epicentre sits above this source area: the deep structure where this area's earthquakes can originate.

estimated maximum magnitude 7.2between 5 and 20 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
22 km West of Acceglio
18 km West · 12 km
11 years ago
11 Jul 2015, 17:25
1.7
11 years ago
5 Jul 2015, 15:37
1.6
4 km South-West of Canosio
15 km South-East · 10 km
11 years ago
15 Jul 2015, 09:34
1.4
4 km East of Celle di Macra
25 km East · 12 km
11 years ago
3 Jul 2015, 23:39
1.6
4 km North-West of Pradleves
25 km East · 14 km
11 years ago
3 Jul 2015, 13:40
1.2
19 km West of Acceglio
15 km West · 11 km
11 years ago
18 Jul 2015, 12:34
1.2
19 km West of Acceglio
15 km West · 16 km
11 years ago
18 Jul 2015, 14:19
2.4
20 km West of Acceglio
16 km West · 9 km
11 years ago
19 Jul 2015, 06:10
1.7
19 km West of Acceglio
15 km West · 10 km
11 years ago
19 Jul 2015, 06:12
2.6
24 km West of Acceglio
20 km West · 13 km
11 years ago
19 Jul 2015, 06:15

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).