All earthquakes
4.1
moderate
EARTHQUAKE DETAILS

Slovenia (SLOVENIA)

21 months ago · 9 Dec, 03:37

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

No. 20 of the year in ItalyStronger than 99% of Italian events in the past yearNo. 3 of the year in Friuli-Venezia GiuliaThe strongest of the past 12 months within 50 km

Where

Slovenia (SLOVENIA)Earthquakes in the province of UdineEarthquakes in Friuli-Venezia Giulia

Epicentre at sea

The epicentre is at sea: for the same magnitude, the shaking is felt less on land, because the energy fades along the way before reaching the coast.

How far away could it be felt?

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

  • up to ~1 km · clearly felt by almost everyone
  • up to ~21 km · felt by many people, especially on upper floors
  • up to ~49 km · felt only by some, at rest

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

3 events
Magnitude:lightweakmoderatestrong

The energy released

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

21tof TNT equivalent
89 lightning bolts
M3
×45 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 ≈ 35 s

Animation sped up ~7× compared to reality.

  • Gorizia
    53 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Trieste
    66 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 s
  • Udine
    75 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 s
  • Pordenone
    123 km from the epicentre
    first tremor in ~21 s
    main shaking in ~35 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?

Isolated quake

In the 30 days around this event no other quakes were recorded within 30 km: a one-off episode, very common in Italy.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
1 before1 after
this quake
Strongest of the sequence2.6

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.

18956.0
Ljubljana earthquake
14 April 1895 · 22 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
19265.7
Carniola interna earthquake
1 January 1926 · 41 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19985.6
Slovenia nord-occidentale earthquake
12 April 1998 · 50 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
16915.3
Ljubljana earthquake
19 February 1691 · 18 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

Tolmin-Idrija

The epicentre lies about 19 km from Tolmin-Idrija, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.2between 1 and 14 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

2.6
Slovenia (SLOVENIA)
15 km South · 8 km
20 months ago
23 Dec, 02:37
1.6
22 months ago
15 Nov, 03:19

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).

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