All earthquakes
1.8
very light
EARTHQUAKE DETAILS

Costa Siciliana centro-settentrionale (Palermo)

55 months ago · 18 Feb, 11:08

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 82% of Italian events in the past year

Where

Costa Siciliana centro-settentrionale (Palermo)Earthquakes in the province of PalermoEarthquakes in Sicilia

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.

7.6kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×63 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.

  • Bagheria
    26 km from the epicentre
    first tremor in ~4 s
    main shaking in ~8 s
  • Palermo
    30 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Caltanissetta
    97 km from the epicentre
    first tremor in ~16 s
    main shaking in ~28 s
  • Trapani
    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

5 km
shallow

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

shallower than the area average (~12 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, 55 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.0
The mainshock
Tirreno Meridionale [Mare]
55 months ago · 17 Feb, 21:23
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 sequence2.0

How often does it happen here?

about every ~24 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 177 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.

20025.9
Tirreno meridionale earthquake
6 September 2002 · 11 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
17265.5
Tirreno meridionale earthquake
1 September 1726 · 29 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
19405.3
Tirreno meridionale earthquake
15 January 1940 · 28 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
20025.1
Tirreno meridionale earthquake
27 September 2002 · 13 km from here

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

The closest seismic structure

Southern Tyrrhenian S

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

estimated maximum magnitude 7.0between 3 and 16 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

2.0
Tirreno Meridionale [Mare]
24 km North-East · 15 km
55 months ago
17 Feb, 21:23
1.6
55 months ago
19 Feb, 11:14

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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