All earthquakes
0.7
very light
EARTHQUAKE DETAILS

M0.7 earthquake · 1 km West of Roaschia (CN)

11 years ago · 20 Aug 2015, 09:44

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 11% of Italian events in the past year

Where

1 km West of RoaschiaEarthquakes 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

21 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.2kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×2,818 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 ≈ 24 s

Animation sped up ~4× compared to reality.

  • Cuneo
    21 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Sanremo
    53 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Savona
    82 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 s
  • Moncalieri
    84 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 (~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?

Foreshock

In hindsight it was a foreshock: 11 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
13 km South-West of Valdieri
11 years ago · 14 Sept 2015, 23:36
Activity in the area right now (30 km radius)
0
last 24 hours
6
last 7 days
11
last 30 days
11 before9 after
this quake
Strongest of the sequence2.5

How often does it happen here?

about every ~27 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 158 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 · 28 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 34 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 33 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19194.9
Alpi Marittime earthquake
28 November 1919 · 27 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

Southern Piemonte

The epicentre lies about 41 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

1.3
2 km West of Bernezzo
16 km North · 24 km
11 years ago
23 Aug 2015, 09:24
1.7
3 km North-West of Pradleves
27 km North-West · 12 km
11 years ago
14 Aug 2015, 13:45
0.9
3 km North-West of Demonte
20 km North-West · 11 km
11 years ago
13 Aug 2015, 21:59
1.0
3 km South of Cartignano
27 km North-West · 14 km
11 years ago
12 Aug 2015, 01:00
0.8
8 km South-West of Valdieri
17 km West · 11 km
11 years ago
30 Aug 2015, 03:23
1.3
4 km East of Pradleves
21 km North-West · 9 km
11 years ago
9 Aug 2015, 21:44
0.9
2 km West of Rittana
15 km North-West · 10 km
11 years ago
31 Aug 2015, 05:29
0.9
1 km South of Valloriate
12 km North-West · 8 km
11 years ago
7 Aug 2015, 05:32
1.6
2 km West of Robilante
6 km North-East · 7 km
11 years ago
6 Aug 2015, 08:12
1.2
6 km West of Triora
29 km South-East · 7 km
11 years ago
3 Sept 2015, 12:48

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).