All earthquakes
0.8
very light
EARTHQUAKE DETAILS

6 km North-East of Altare

18 months ago · 12 Mar, 11:30

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

6 km North-East of AltareEarthquakes 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

29 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 ≈ 19 s

Animation sped up ~3× compared to reality.

  • Savona
    10 km from the epicentre
    first tremor in ~2 s
    main shaking in ~4 s
  • Genova
    39 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Asti
    62 km from the epicentre
    first tremor in ~11 s
    main shaking in ~18 s
  • Alessandria
    64 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 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

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

in line with 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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.0, 18 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.0
The mainshock
1 km South of Cortemilia
18 months ago · 28 Feb, 08:40
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
3
last 30 days
22 before6 after
this quake
Strongest of the sequence2.0

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: 35 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.

17675.0
Genovese earthquake
7 February 1767 · 33 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 · 43 km from here
12764.8
Monferrato earthquake
29 July 1276 · 31 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
15374.6
Savona earthquake
November 1537 · 11 km from here
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 25 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
2 km South-West of Cortemilia
27 km North-West · 9 km
18 months ago
11 Mar, 04:58
1.3
1 km South-East of Bergolo
24 km North-West · 8 km
18 months ago
15 Mar, 00:38
1.1
1 km South of Cortemilia
26 km North-West · 9 km
18 months ago
15 Mar, 00:40
1.5
1 km West of Perletto
28 km North-West · 11 km
18 months ago
8 Mar, 20:13
1.0
2 km North-West of Bergolo
27 km North-West · 6 km
18 months ago
8 Mar, 11:42
1.7
1 km South-West of Cortemilia
26 km North-West · 9 km
18 months ago
8 Mar, 11:24
0.8
18 months ago
7 Mar, 11:32
0.9
11 km East of Bergeggi
22 km South-East · 16 km
18 months ago
17 Mar, 12:56
1.4
1 km South-East of Cortemilia
25 km North-West · 10 km
18 months ago
6 Mar, 09:28
1.7
2 km West of Cortemilia
28 km North-West · 14 km
18 months ago
2 Mar, 13:05

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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