All earthquakes
1.3
very light
EARTHQUAKE DETAILS

M1.3 earthquake · 6 km South of Mazzarrone (CT)

6 years ago · 21 Mar 2020, 04:23

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

Stronger than 55% of Italian events in the past year

Where

6 km South of MazzarroneEarthquakes in the province of CataniaEarthquakes 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

5 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×355 its energy
M0this quakeM2

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 ≈ 9 s

Animation sped up ~2× compared to reality.

  • Vittoria
    11 km from the epicentre
    first tremor in ~3 s
    main shaking in ~6 s
  • Ragusa
    15 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Gela
    26 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Modica
    28 km from the epicentre
    first tremor in ~6 s
    main shaking in ~9 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
2 times the height of Mount Everest

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

in line with the area average (~20 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 (M2.5, 6 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.5
The mainshock
3 km South of Monterosso Almo
6 years ago · 9 Mar 2020, 07:05
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
16
last 30 days
4 before0 after
this quake
Strongest of the sequence2.5

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: 176 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.

16937.3
Sicilia sud-orientale earthquake
11 January 1693 · 41 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
15426.7
Sicilia sud-orientale earthquake
10 December 1542 · 39 km from here
XCompletely destructive: most buildings are destroyed.
11696.5
Sicilia sud-orientale earthquake
4 February 1169 · 39 km from here
XCompletely destructive: most buildings are destroyed.
16936.1
Sicilia sud-orientale earthquake
9 January 1693 · 43 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

Ragusa-Palagonia

The epicentre lies about 13 km from Ragusa-Palagonia, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.9between 1 and 23 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
6 km South of Grammichele
16 km North · 19 km
6 years ago
9 Mar 2020, 23:17
2.2
1 km West of Monterosso Almo
14 km East · 16 km
6 years ago
9 Mar 2020, 09:40
2.5
6 years ago
9 Mar 2020, 07:05
1.6
6 km North-West of Vizzini
27 km North-East · 21 km
6 years ago
26 Feb 2020, 20:35

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).