All earthquakes
1.5
very light
EARTHQUAKE DETAILS

5 km South of San Mauro Castelverde

5 months ago · 21 Mar, 20:14

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

Stronger than 68% of Italian events in the past year

Where

5 km South of San Mauro CastelverdeEarthquakes in the province of PalermoEarthquakes in Sicilia

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

47 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 ≈ 26 s

Animation sped up ~5× compared to reality.

  • Caltanissetta
    50 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Bagheria
    68 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 s
  • Catania
    84 km from the epicentre
    first tremor in ~15 s
    main shaking in ~25 s
  • Palermo
    84 km from the epicentre
    first tremor in ~15 s
    main shaking in ~26 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

30 km
medium depth
3.4 times the height of Mount Everest

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

deeper than the area average (~18 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 (M4.2, 5 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

4.2
The mainshock
3 km East of Pettineo
5 months ago · 21 Mar, 19:04
Activity in the area right now (30 km radius)
0
last 24 hours
2
last 7 days
16
last 30 days
21 before25 after
this quake
Strongest of the sequence4.2

How often does it happen here?

about every ~6 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 754 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.

18235.8
Sicilia settentrionale earthquake
5 March 1823 · 35 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18195.4
Monti Madonie earthquake
24 February 1819 · 18 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
18185.3
Monti Madonie earthquake
8 September 1818 · 16 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19675.3
Monti Nebrodi earthquake
31 October 1967 · 16 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.

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

The closest seismic structure

Southern Tyrrhenian S

The epicentre lies about 56 km from Southern Tyrrhenian S, one of the seismic structures mapped by INGV geologists.

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

2.7
5 km South of Reitano
10 km North-East · 27 km
5 months ago
21 Mar, 20:10
2.8
5 km North-West of Mistretta
10 km North-East · 22 km
5 months ago
21 Mar, 20:09
2.0
5 km North-West of Mistretta
12 km North-East · 9 km
5 months ago
21 Mar, 20:23
2.5
2 km North-West of Mistretta
11 km East · 10 km
5 months ago
21 Mar, 20:24
1.9
4 km South of Reitano
12 km North-East · 10 km
5 months ago
21 Mar, 20:27
1.9
5 months ago
21 Mar, 19:49
1.8
3 km East of Pettineo
9 km North-East · 23 km
5 months ago
21 Mar, 19:49
1.4
5 km South of Reitano
11 km North-East · 11 km
5 months ago
21 Mar, 20:48
1.8
5 months ago
21 Mar, 20:54
1.9
3 km North-East of Pettineo
10 km North-East · 31 km
5 months ago
21 Mar, 19:30

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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