All earthquakes
2.1
light
EARTHQUAKE DETAILS

0 km East of Rossiglione

62 months ago · 27 Jul, 22:18

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

Stronger than 90% of Italian events in the past year

Where

0 km East of RossiglioneEarthquakes in the province of GenovaEarthquakes 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

15 events
Magnitude:lightweakmoderatestrong

The energy released

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

21kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×22 its energy
M1this quakeM3

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 ≈ 16 s

Animation sped up ~3× compared to reality.

  • Genova
    21 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Savona
    31 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Alessandria
    40 km from the epicentre
    first tremor in ~7 s
    main shaking in ~12 s
  • Asti
    54 km from the epicentre
    first tremor in ~9 s
    main shaking in ~16 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

10 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?

Foreshock

In hindsight it was a foreshock: 61 months ago the same area had a stronger quake (M2.4). This can only be said after the fact — it was not predictable beforehand.

2.4
The mainshock
1 km East of Casella
61 months ago · 26 Aug, 21:16
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
1
last 30 days
1 before13 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~59 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 72 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.

18285.7
Oltrepò Pavese earthquake
9 October 1828 · 43 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
15415.3
Valle Scrivia earthquake
22 October 1541 · 30 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19455.1
Oltrepò Pavese earthquake
29 June 1945 · 48 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16805.1
Valle Scrivia earthquake
30 April 1680 · 19 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.

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

The closest seismic structure

Imperia Promontory

The epicentre lies about 38 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

0.7
1 km East of Savignone
27 km East · 13 km
62 months ago
26 Jul, 22:50
1.3
2 km North of Savignone
27 km East · 10 km
62 months ago
30 Jul, 07:03
1.3
2 km North of Rossiglione
2 km North · 10 km
62 months ago
31 Jul, 00:34
1.6
2 km North of Savignone
27 km East · 9 km
62 months ago
7 Aug, 15:53
1.6
1 km East of Casella
28 km East · 9 km
61 months ago
10 Aug, 00:05
1.3
61 months ago
19 Aug, 06:39
1.9
1 km North-East of Casella
27 km East · 10 km
61 months ago
20 Aug, 05:47
1.3
1 km North of Savignone
26 km East · 9 km
61 months ago
20 Aug, 05:55
0.9
1 km South-East of Busalla
26 km East · 9 km
61 months ago
20 Aug, 09:06
1.1
1 km North-West of Savignone
25 km East · 10 km
61 months ago
20 Aug, 12:45

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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