All earthquakes
0.8
very light
EARTHQUAKE DETAILS

1 km South-West of Bergeggi

121 months ago · 9 Sept, 16:00

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 16% of Italian events in the past year

Where

1 km South-West of BergeggiEarthquakes in the province of SavonaEarthquakes in Liguria

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

6 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 ×1,995 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 ≈ 21 s

Animation sped up ~4× compared to reality.

  • Savona
    10 km from the epicentre
    first tremor in ~2 s
    main shaking in ~3 s
  • Genova
    39 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Sanremo
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Cuneo
    74 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 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

1 km
shallow

At only a few km deep the shaking is felt more sharply at the surface.

shallower than the area average (~7 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: 121 months ago the same area had a stronger quake (M1.7). This can only be said after the fact — it was not predictable beforehand.

1.7
The mainshock
14 km East of Albenga
121 months ago · 20 Sept, 07:28
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
5
last 30 days
2 before3 after
this quake
Strongest of the sequence1.7

How often does it happen here?

about every ~4 months

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 38 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.

18185.3
Liguria occidentale earthquake
23 February 1818 · 47 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
17675.0
Genovese earthquake
7 February 1767 · 40 km from here
VI-VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19684.9
Liguria occidentale earthquake
18 April 1968 · 38 km from here
12764.8
Monferrato earthquake
29 July 1276 · 44 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

Imperia Promontory

The epicentre lies about 11 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

1.7
14 km East of Albenga
26 km South · 7 km
121 months ago
20 Sept, 07:28
1.2
2 km South of Altare
12 km North-West · 11 km
122 months ago
25 Aug, 16:09
1.0
2 km West of Quiliano
9 km North-West · 11 km
121 months ago
27 Sept, 16:05
1.0
24 km South-East of Noli
24 km South-East · 15 km
122 months ago
18 Aug, 02:20
1.3
4 km South-East of Bergeggi
4 km South-East · 1 km
120 months ago
7 Oct, 11:44

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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