All earthquakes
3.3
weak
EARTHQUAKE DETAILS

8 km North-West of Rocchetta Nervina

121 months ago · 3 Sept, 21:14

A weak earthquake, felt by some of the population. At this depth the shaking is felt, but rarely causes damage.

Stronger than 99% of Italian events in the past yearNo. 1 of the year in LiguriaThe strongest of the past 12 months within 50 km

Where

8 km North-West of Rocchetta NervinaEarthquakes in the province of ImperiaEarthquakes in Liguria

How far away could it be felt?

An estimate of how far people may have felt this quake.

  • up to ~15 km · felt only by some, at rest
    ≈ 29,000 people live in this area

The coloured rings on the map below show these distances.

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

8 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3tof TNT equivalent
5.6 lightning bolts
M3
×2.8 the energy of a magnitude 3 earthquake
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 ≈ 33 s

Animation sped up ~6× compared to reality.

  • Sanremo
    25 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Cuneo
    52 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Savona
    87 km from the epicentre
    first tremor in ~15 s
    main shaking in ~25 s
  • Moncalieri
    115 km from the epicentre
    first tremor in ~19 s
    main shaking in ~33 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

14 km
medium depth
1.6 times the height of Mount Everest

At this depth the shaking is felt, but rarely causes damage.

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?

Isolated quake

In the 30 days around this event no other quakes were recorded within 30 km: a one-off episode, very common in Italy.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
5
last 30 days
3 before4 after
this quake
Strongest of the sequence1.9

How often does it happen here?

about every ~17 months

Within 50 km of this epicentre, a magnitude ≥ 3 earthquake has occurred on average this often: 8 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.

18876.3
Liguria occidentale earthquake
23 February 1887 · 40 km from here
XCompletely destructive: most buildings are destroyed.
15645.8
Lantosque earthquake
20 July 1564 · 20 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16445.7
Alpes Niçoises earthquake
15 February 1644 · 22 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16185.6
Alpes Niçoises earthquake
18 January 1618 · 16 km from here
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

Imperia Promontory

The epicentre lies about 31 km from Imperia Promontory, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.4between 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

1.0
3 km South of Limone Piemonte
25 km North · 10 km
121 months ago
12 Sept, 22:04
1.1
121 months ago
16 Sept, 18:41
1.4
3 km East of Seborga
22 km South-East · 8 km
122 months ago
19 Aug, 02:13
1.4
4 km West of Briga Alta
26 km North-East · 9 km
121 months ago
22 Sept, 12:17
1.4
2 km North-East of Triora
21 km East · 9 km
121 months ago
27 Sept, 16:15
1.5
2 km East of Entracque
27 km North · 13 km
122 months ago
10 Aug, 15:17
1.9
3 km East of Seborga
22 km South-East · 10 km
122 months ago
9 Aug, 08:05

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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