All earthquakes
1.5
very light
EARTHQUAKE DETAILS

M1.5 offshore earthquake

8 years ago · 19 Jun 2018, 05:35

A very light earthquake, probably not felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 69% of Italian events in the past year

Where

Nearest Italian town: Laigueglia (SV)Earthquakes in the province of SavonaEarthquakes 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

6 events
Magnitude:lightweakmoderatestrong

The energy released

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

2.7kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×178 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 ≈ 28 s

Animation sped up ~5× compared to reality.

  • Savona
    47 km from the epicentre
    first tremor in ~8 s
    main shaking in ~14 s
  • Sanremo
    60 km from the epicentre
    first tremor in ~10 s
    main shaking in ~18 s
  • Genova
    64 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 s
  • Cuneo
    97 km from the epicentre
    first tremor in ~16 s
    main shaking in ~28 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

17 km
medium depth
1.9 times the height of Mount Everest

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

deeper than the area average (~8 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: 8 years ago the same area had a stronger quake (M2.1). This can only be said after the fact — it was not predictable beforehand.

2.1
The mainshock
Costa Ligure centro-occidentale (Savona)
8 years ago · 15 Jul 2018, 14:00
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
2 before3 after
this quake
Strongest of the sequence2.1

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: 32 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 · 43 km from here
XCompletely destructive: most buildings are destroyed.
18185.3
Liguria occidentale earthquake
23 February 1818 · 39 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19635.0
Mar Ligure earthquake
27 July 1963 · 49 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
19684.9
Liguria occidentale earthquake
18 April 1968 · 43 km from here

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

1.4
23 km South-East of Noli
23 km North-East · 10 km
8 years ago
21 Jun 2018, 09:11
1.3
Costa Ligure centro-occidentale (Savona)
18 km East · 14 km
8 years ago
14 Jun 2018, 21:40
1.3
20 km South-East of Noli
20 km North · 7 km
8 years ago
26 Jun 2018, 05:46
1.0
Costa Ligure centro-occidentale (Savona)
16 km North-East · 11 km
8 years ago
7 Jun 2018, 12:06
2.1
Costa Ligure centro-occidentale (Savona)
21 km North-East · 11 km
8 years ago
15 Jul 2018, 14:00

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).