All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake outside Italy

5 years ago · 2 Jul 2021, 02:54

A very light earthquake, probably not felt by people. At only a few km deep the shaking is felt more sharply at the surface.

Where

Nearest Italian town: Gorizia (GO)Earthquakes in the province of GoriziaEarthquakes 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?

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 ≈ 38 s

Animation sped up ~7× compared to reality.

  • Trieste
    39 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Udine
    50 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Pordenone
    96 km from the epicentre
    first tremor in ~16 s
    main shaking in ~28 s
  • Treviso
    133 km from the epicentre
    first tremor in ~22 s
    main shaking in ~38 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

7 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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.0, 5 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.0
The mainshock
22 km East of Gorizia
5 years ago · 1 Jul 2021, 12:50
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
3 before1 after
this quake
Strongest of the sequence2.0

How often does it happen here?

about every ~35 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 122 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.

19265.7
Carniola interna earthquake
1 January 1926 · 38 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19985.6
Slovenia nord-occidentale earthquake
12 April 1998 · 43 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
14035.6
Cividale del Friuli earthquake
6 September 1403 · 38 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
16915.3
Ljubljana earthquake
19 February 1691 · 45 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

Vipava

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

estimated maximum magnitude 6.7between 1 and 12 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

1.8
22 km East of Gorizia
1 km West · 13 km
5 years ago
2 Jul 2021, 02:04
2.0
22 km East of Gorizia
1 km West · 15 km
5 years ago
1 Jul 2021, 12:50
1.2
Confine Italia-Slovenia (SLOVENIA)
4 km East · 11 km
5 years ago
3 Jul 2021, 04:37
1.0
12 km South-East of Stregna
17 km West · 7 km
5 years ago
23 Jun 2021, 13:59

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).