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EARTHQUAKE DETAILS

M2.5 earthquake · 3 km South-West of Robilante (CN)

10 years ago · 24 May 2016, 21:46

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

Stronger than 95% of Italian events in the past year

Where

3 km South-West of RobilanteEarthquakes 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

22 events
Magnitude:lightweakmoderatestrong

The energy released

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

85kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×5.6 its energy
M2this quakeM4

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 ≈ 23 s

Animation sped up ~4× compared to reality.

  • Cuneo
    17 km from the epicentre
    first tremor in ~3 s
    main shaking in ~6 s
  • Sanremo
    52 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Savona
    77 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 s
  • Moncalieri
    81 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 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
1.1 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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by 12 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
6
last 7 days
11
last 30 days
9 before12 after
this quake
Strongest of the sequence2.3

How often does it happen here?

about every ~3 months

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 41 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 · 32 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 38 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 37 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19684.9
Liguria occidentale earthquake
18 April 1968 · 49 km from here

Source: Parametric Catalogue of Italian Earthquakes CPTI15 (INGV, CC BY 4.0).

The closest seismic structure

Southern Piemonte

The epicentre lies about 39 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

1.1
1 km West of Robilante
3 km North · 1 km
10 years ago
26 May 2016, 11:37
1.4
4 km East of Pradleves
22 km North-West · 9 km
10 years ago
20 May 2016, 22:36
1.4
2 km North-East of Pradleves
27 km North-West · 11 km
10 years ago
28 May 2016, 21:23
1.2
2 km South-East of Monterosso Grana
18 km North-West · 14 km
10 years ago
19 May 2016, 22:30
1.9
2 km South of Castelmagno
28 km North-West · 6 km
10 years ago
19 May 2016, 16:14
0.9
3 km North-East of Monterosso Grana
21 km North-West · 6 km
10 years ago
30 May 2016, 11:16
1.0
2 km South-West of Valgrana
18 km North-West · 11 km
10 years ago
3 Jun 2016, 01:58
1.2
3 km North-West of Roccasparvera
13 km North-West · 11 km
10 years ago
3 Jun 2016, 10:38
0.6
1 km East of Montemale di Cuneo
21 km North-West · 6 km
10 years ago
4 Jun 2016, 05:49
1.2
2 km North-West of Monterosso Grana
22 km North-West · 12 km
10 years ago
4 Jun 2016, 17:10

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).