All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake · 1 km North-East of Loculi (NU)

5 years ago · 23 Jul 2021, 09:37

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 74% of Italian events in the past year

Where

1 km North-East of LoculiEarthquakes in the province of NuoroEarthquakes in Sardegna

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

1 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 ≈ 40 s

Animation sped up ~8× compared to reality.

  • Olbia
    54 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Sassari
    110 km from the epicentre
    first tremor in ~18 s
    main shaking in ~31 s
  • Quartu Sant'Elena
    137 km from the epicentre
    first tremor in ~23 s
    main shaking in ~39 s
  • Cagliari
    141 km from the epicentre
    first tremor in ~23 s
    main shaking in ~40 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

1 km
shallow

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

shallower than the area average (~8 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

No other quakes within 30 km in the 30 days around the event.

The closest seismic structure

Northern Africa offshore - East

The epicentre lies about 208 km from Northern Africa offshore - East, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 8.0between 1 and 25 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).

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).