All earthquakes
1.0
very light
EARTHQUAKE DETAILS

3 km West of Forni di Sopra

26 months ago · 21 Jul, 00:40

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 30% of Italian events in the past year

Where

3 km West of Forni di SopraEarthquakes in the province of UdineEarthquakes in Friuli-Venezia Giulia

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

12 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.5kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×1,000 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 ≈ 26 s

Animation sped up ~5× compared to reality.

  • Pordenone
    55 km from the epicentre
    first tremor in ~9 s
    main shaking in ~16 s
  • Udine
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Treviso
    87 km from the epicentre
    first tremor in ~15 s
    main shaking in ~25 s
  • Bolzano
    89 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

6 km
shallow

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

in line with the area average (~9 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: 25 months ago the same area had a stronger quake (M1.9). This can only be said after the fact — it was not predictable beforehand.

1.9
The mainshock
1 km South-West of Enemonzo
25 months ago · 14 Aug, 14:41
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
6
last 30 days
5 before6 after
this quake
Strongest of the sequence1.9

How often does it happen here?

about every ~20 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 214 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.

18736.3
Alpago Cansiglio earthquake
29 June 1873 · 32 km from here
IX-XCompletely destructive: most buildings are destroyed.
19366.1
Alpago Cansiglio earthquake
18 October 1936 · 39 km from here
IXDestructive: many buildings partly or fully collapse.
19286.0
Carnia earthquake
27 March 1928 · 35 km from here
IXDestructive: many buildings partly or fully collapse.
17946.0
Prealpi Friulane earthquake
7 June 1794 · 26 km from here
IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Tramonti-Montemaggiore

The epicentre lies about 20 km from Tramonti-Montemaggiore, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.2between 1 and 6 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

1.5
25 months ago
26 Jul, 02:33
0.7
3 km South-East of Socchieve
23 km East · 10 km
26 months ago
13 Jul, 22:01
0.4
2 km North-West of Andreis
23 km South · 6 km
25 months ago
28 Jul, 10:15
1.6
6 km North of Tramonti di Sopra
20 km South-East · 8 km
25 months ago
29 Jul, 11:32
0.8
1 km South-East of Tramonti di Sotto
28 km South-East · 7 km
26 months ago
5 Jul, 06:39
1.7
26 months ago
30 Jun, 20:51
1.9
1 km South-West of Enemonzo
26 km East · 6 km
25 months ago
14 Aug, 14:41
0.7
2 km South-West of Enemonzo
25 km East · 5 km
25 months ago
14 Aug, 16:07
0.7
25 months ago
17 Aug, 05:07
1.3
4 km North-West of Chies d'Alpago
27 km South-West · 9 km
26 months ago
23 Jun, 06:51

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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