All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake · 2 km West of Vallelonga (VV)

5 years ago · 11 Sept 2021, 16:38

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

2 km West of VallelongaEarthquakes in the province of Vibo ValentiaEarthquakes in Calabria

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

13 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 ≈ 22 s

Animation sped up ~4× compared to reality.

  • Lamezia Terme
    35 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Catanzaro
    39 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Cosenza
    71 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 s
  • Reggio di Calabria
    78 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 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.

shallower than the area average (~17 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: 5 years ago the same area had a stronger quake (M2.4). This can only be said after the fact — it was not predictable beforehand.

2.4
The mainshock
3 km South-West of Vallelonga
5 years ago · 12 Sept 2021, 04:06
Activity in the area right now (30 km radius)
1
last 24 hours
1
last 7 days
26
last 30 days
6 before6 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~9 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 456 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.

17837.1
Calabria meridionale earthquake
5 February 1783 · 47 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
16387.1
Calabria centrale earthquake
27 March 1638 · 45 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
17837.0
Calabria centrale earthquake
28 March 1783 · 22 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
19057.0
Calabria centrale earthquake
8 September 1905 · 31 km from here
X-XICatastrophic: very few buildings remain standing; landslides and ground cracks.

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

The closest seismic structure

Serre

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

estimated maximum magnitude 7.2between 3 and 11 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

1.2
3 km West of Vallelonga
1 km West · 5 km
5 years ago
12 Sept 2021, 03:09
2.4
3 km South-West of Vallelonga
1 km South-West · 9 km
5 years ago
12 Sept 2021, 04:06
1.0
3 km West of Vallelonga
1 km West · 5 km
5 years ago
12 Sept 2021, 05:07
1.1
4 km North-West of Maida
30 km North · 10 km
5 years ago
9 Sept 2021, 15:51
1.5
2 km North of San Calogero
25 km West · 17 km
5 years ago
9 Sept 2021, 14:22
2.3
5 years ago
9 Sept 2021, 14:05
1.3
3 km North-West of Maida
30 km North · 10 km
5 years ago
7 Sept 2021, 20:21
1.7
0 km South-West of Maropati
28 km South-West · 16 km
5 years ago
30 Aug 2021, 02:53
0.8
2 km West of Dasà
14 km South-West · 11 km
5 years ago
27 Sept 2021, 17:51
1.0
1 km North-East of Candidoni
26 km South-West · 13 km
5 years ago
30 Sept 2021, 08:20

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).