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EARTHQUAKE DETAILS

11 km East of Riposto

61 months ago · 30 Aug, 18:49

A light earthquake, rarely felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 97% of Italian events in the past year

Where

11 km East of RipostoEarthquakes 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

50 events
Magnitude:lightweakmoderatestrong

The energy released

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

169kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×2.8 its energy
M2this quakeM4

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 ≈ 16 s

Animation sped up ~3× compared to reality.

  • Acireale
    17 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Catania
    37 km from the epicentre
    first tremor in ~7 s
    main shaking in ~12 s
  • Messina
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~16 s
  • Reggio di Calabria
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~16 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

16 km
medium depth
1.8 times the height of Mount Everest

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

in line with 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?

Foreshock

In hindsight it was a foreshock: 60 months ago the same area had a stronger quake (M3.0). This can only be said after the fact — it was not predictable beforehand.

3.0
The mainshock
2 km South of Mascali
60 months ago · 10 Sept, 19:21
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
18
last 30 days
20 before29 after
this quake
Strongest of the sequence3.0

How often does it happen here?

about every ~7 days

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 591 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.

18186.3
Catanese earthquake
20 February 1818 · 21 km from here
IX-XCompletely destructive: most buildings are destroyed.
17866.1
Golfo di Patti earthquake
10 March 1786 · 49 km from here
IXDestructive: many buildings partly or fully collapse.
19905.6
Sicilia sud-orientale earthquake
13 December 1990 · 48 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
17805.5
Sicilia nord-orientale earthquake
28 March 1780 · 16 km from here
VII-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

Gela-Catania

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

estimated maximum magnitude 7.1between 3 and 10 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

2.5
11 km East of Riposto
1 km West · 17 km
61 months ago
30 Aug, 19:03
1.0
7 km West of Sant'Alfio
29 km West · 0 km
61 months ago
2 Sept, 07:52
1.8
14 km East of Aci Castello
18 km South · 27 km
61 months ago
26 Aug, 09:38
1.2
8 km West of Sant'Alfio
29 km West · 0 km
61 months ago
25 Aug, 22:40
1.2
7 km West of Sant'Alfio
28 km West · 2 km
61 months ago
24 Aug, 06:13
1.8
61 months ago
23 Aug, 20:53
1.5
61 months ago
23 Aug, 19:49
1.2
1 km North-West of Mascali
14 km West · 4 km
61 months ago
7 Sept, 04:51
1.3
2 km South-West of Milo
20 km West · 8 km
61 months ago
8 Sept, 15:08
1.4
8 km West of Sant'Alfio
29 km West · 1 km
61 months ago
21 Aug, 18:52

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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