All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake · 8 km West of Avola (SR)

9 years ago · 3 May 2017, 13:54

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 74% of Italian events in the past year

Where

8 km West of AvolaEarthquakes 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.

3.8kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×126 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 ≈ 14 s

Animation sped up ~3× compared to reality.

  • Modica
    19 km from the epicentre
    first tremor in ~3 s
    main shaking in ~6 s
  • Siracusa
    19 km from the epicentre
    first tremor in ~3 s
    main shaking in ~6 s
  • Ragusa
    34 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Vittoria
    49 km from the epicentre
    first tremor in ~8 s
    main shaking in ~14 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

8 km
shallow

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

shallower 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?

Foreshock

In hindsight it was a foreshock: 9 years ago the same area had a stronger quake (M2.8). This can only be said after the fact — it was not predictable beforehand.

2.8
The mainshock
7 km North of Ispica
9 years ago · 26 May 2017, 18:11
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
17
last 30 days
1 before3 after
this quake
Strongest of the sequence2.8

How often does it happen here?

about every ~21 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 209 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 · 22 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
15426.7
Sicilia sud-orientale earthquake
10 December 1542 · 32 km from here
XCompletely destructive: most buildings are destroyed.
11696.5
Sicilia sud-orientale earthquake
4 February 1169 · 32 km from here
XCompletely destructive: most buildings are destroyed.
16936.1
Sicilia sud-orientale earthquake
9 January 1693 · 22 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

Monte Lauro

The epicentre lies about 16 km from Monte Lauro, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.0between 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

2.0
6 km East of Canicattini Bagni
12 km North-East · 8 km
9 years ago
24 Apr 2017, 07:41
1.4
4 km East of Floridia
18 km North-East · 25 km
9 years ago
26 May 2017, 03:38
1.9
6 km South of Noto
18 km South · 2 km
9 years ago
26 May 2017, 17:05
2.8
7 km North of Ispica
20 km South-West · 28 km
9 years ago
26 May 2017, 18:11

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).