All earthquakes
1.3
very light
EARTHQUAKE DETAILS

4 km South-East of Bergeggi

120 months ago · 7 Oct, 11:44

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 55% of Italian events in the past year

Where

4 km South-East 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

9 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 ≈ 22 s

Animation sped up ~4× compared to reality.

  • Savona
    12 km from the epicentre
    first tremor in ~2 s
    main shaking in ~4 s
  • Genova
    38 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
    77 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 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: 120 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
21 km East of Bergeggi
120 months ago · 17 Oct, 08:53
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
4
last 30 days
4 before4 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: 37 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 · 42 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 · 39 km from here
12764.8
Monferrato earthquake
29 July 1276 · 47 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 7 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

1.4
120 months ago
5 Oct, 10:00
1.0
2 km West of Quiliano
13 km North-West · 11 km
121 months ago
27 Sept, 16:05
1.7
21 km East of Bergeggi
18 km East · 12 km
120 months ago
17 Oct, 08:53
0.9
3 km South-East of Bergeggi
2 km North · 1 km
120 months ago
19 Oct, 10:23
1.1
120 months ago
19 Oct, 15:52
1.7
14 km East of Albenga
24 km South-West · 7 km
121 months ago
20 Sept, 07:28
0.8
1 km South-West of Bergeggi
4 km North-West · 1 km
121 months ago
9 Sept, 16:00
0.7
119 months ago
4 Nov, 17:01

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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