All earthquakes
1.9
very light
EARTHQUAKE DETAILS

3 km North of Rosolini

25 months ago · 17 Aug, 15:23

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

Stronger than 85% of Italian events in the past year

Where

3 km North of RosoliniEarthquakes in the province of SiracusaEarthquakes 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.

11kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×45 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 ≈ 13 s

Animation sped up ~2× compared to reality.

  • Modica
    6 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Ragusa
    21 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Siracusa
    32 km from the epicentre
    first tremor in ~7 s
    main shaking in ~12 s
  • Vittoria
    37 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 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

27 km
medium depth
3 times the height of Mount Everest

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

deeper than the area average (~19 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: 24 months ago the same area had a stronger quake (M2.2). This can only be said after the fact — it was not predictable beforehand.

2.2
The mainshock
3 km West of Giarratana
24 months ago · 7 Sept, 03:19
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
3
last 30 days
2 before2 after
this quake
Strongest of the sequence2.2

How often does it happen here?

about every ~22 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 198 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 · 28 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
15426.7
Sicilia sud-orientale earthquake
10 December 1542 · 35 km from here
XCompletely destructive: most buildings are destroyed.
11696.5
Sicilia sud-orientale earthquake
4 February 1169 · 35 km from here
XCompletely destructive: most buildings are destroyed.
16936.1
Sicilia sud-orientale earthquake
9 January 1693 · 29 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

Scicli-Giarratana

The epicentre lies about 12 km from Scicli-Giarratana, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.0between 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

1.4
7 km North-East of Rosolini
6 km East · 25 km
25 months ago
11 Aug, 14:37
2.2
3 km West of Giarratana
23 km North-West · 25 km
24 months ago
7 Sept, 03:19
1.8
7 km South of Ragusa
22 km West · 27 km
26 months ago
22 Jul, 06:46
1.4
9 km South of Ragusa
20 km West · 20 km
24 months ago
15 Sept, 03:08

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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