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EARTHQUAKE DETAILS

Costa Ligure Occidentale (Imperia)

100 months ago · 3 Jun, 03:47

A light earthquake, rarely felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 97% of Italian events in the past yearNo. 1 of the year in LiguriaThe strongest of the past 12 months within 50 km

Where

Costa Ligure Occidentale (Imperia)Earthquakes in the province of ImperiaEarthquakes in Liguria

Epicentre at sea

The epicentre is at sea: for the same magnitude, the shaking is felt less on land, because the energy fades along the way before reaching the coast.

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

3 events
Magnitude:lightweakmoderatestrong

The energy released

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

239kgof TNT equivalent
1.0 lightning bolt
M3
A magnitude 3 earthquake releases ×2 its energy
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 ≈ 37 s

Animation sped up ~7× compared to reality.

  • Sanremo
    30 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Cuneo
    96 km from the epicentre
    first tremor in ~17 s
    main shaking in ~28 s
  • Savona
    101 km from the epicentre
    first tremor in ~17 s
    main shaking in ~30 s
  • Genova
    128 km from the epicentre
    first tremor in ~22 s
    main shaking in ~37 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

23 km
medium depth
2.5 times the height of Mount Everest

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

deeper than the area average (~11 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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by one aftershock within 30 km. Aftershocks tend to fade in number and strength over time.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
1 before1 after
this quake
Strongest of the sequence1.0

How often does it happen here?

about every ~8 months

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 18 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 · 41 km from here
XCompletely destructive: most buildings are destroyed.
19636.0
Mar Ligure earthquake
19 July 1963 · 38 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18545.7
Liguria occidentale earthquake
29 December 1854 · 21 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18315.6
Liguria occidentale earthquake
26 May 1831 · 33 km from here
VIII-IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Imperia Promontory

The epicentre sits above this source area: the deep structure where this area's earthquakes can originate.

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
16 km South of Bordighera
12 km North · 8 km
100 months ago
3 Jun, 16:14
1.0
7 km South of Riva Ligure
25 km North-East · 11 km
101 months ago
20 May, 09:34

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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