All earthquakes
4.0
moderate
EARTHQUAKE DETAILS

M4.0 earthquake outside Italy

11 years ago · 29 Aug 2015, 20:47

A moderate earthquake, felt by people in the area. At only a few km deep the shaking is felt more sharply at the surface.

The strongest of the past 12 months within 50 km

Where

Nearest Italian town: Savogna (UD)Earthquakes in the province of UdineEarthquakes in Friuli-Venezia Giulia

Epicentre abroad

The epicentre lies outside Italy's borders. The quake appears here because the INGV seismic network also records events close to Italy, which can be felt on Italian territory.

How far away could it be felt?

An estimate of how far people may have felt this quake.

  • up to ~18 km · felt by many people, especially on upper floors
    ≈ 2,000 people live in this area
  • up to ~44 km · felt only by some, at rest
    ≈ 346,000 people live in this area

The coloured rings on the map below show these distances.

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

14 events
Magnitude:lightweakmoderatestrong

The energy released

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

15tof TNT equivalent
63 lightning bolts
M3
×32 the energy of a magnitude 3 earthquake
M3this quakeM5

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 ≈ 36 s

Animation sped up ~7× compared to reality.

  • Udine
    39 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Trieste
    77 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 s
  • Pordenone
    84 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 s
  • Treviso
    127 km from the epicentre
    first tremor in ~21 s
    main shaking in ~36 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 (~10 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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by 11 aftershocks within 30 km. Aftershocks tend to fade in number and strength over time.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
4
last 30 days
2 before11 after
this quake
Strongest of the sequence2.4

How often does it happen here?

It is the first magnitude ≥ 4 earthquake recorded within 50 km since 2014, the start of our archive.

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.

13486.6
Alpi Giulie earthquake
25 January 1348 · 21 km from here
IX-XCompletely destructive: most buildings are destroyed.
19766.5
Friuli earthquake
6 May 1976 · 37 km from here
IX-XCompletely destructive: most buildings are destroyed.
15116.3
Friuli-Slovenia earthquake
26 March 1511 · 31 km from here
IXDestructive: many buildings partly or fully collapse.
16906.2
Carinthia, Villach earthquake
4 December 1690 · 42 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

Bovec-Tolminka Springs

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

estimated maximum magnitude 6.9between 1 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

1.4
15 km North of Savogna
0 km East · 5 km
11 years ago
29 Aug 2015, 22:49
1.1
15 km North of Savogna
0 km South · 6 km
11 years ago
31 Aug 2015, 05:19
1.0
4 km East of Moggio Udinese
30 km West · 10 km
11 years ago
16 Aug 2015, 21:51
1.0
5 km West of Resia
23 km West · 9 km
11 years ago
16 Aug 2015, 04:31
1.4
16 km North of Savogna
1 km North-West · 7 km
11 years ago
12 Sept 2015, 20:43
1.8
11 years ago
18 Sept 2015, 09:52
1.3
8 km South of Malborghetto Valbruna
17 km North-West · 9 km
11 years ago
18 Sept 2015, 09:54
2.4
15 km North of Savogna
0 km South · 5 km
11 years ago
23 Sept 2015, 03:53
1.5
13 km North of Savogna
2 km South · 7 km
11 years ago
25 Sept 2015, 12:26
2.0
5 km North-East of Chiusaforte
23 km North-West · 6 km
11 years ago
27 Sept 2015, 06:19

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).