All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake · 3 km South of San Basile (CS)

5 years ago · 25 Apr 2021, 12:06

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

3 km South of San BasileEarthquakes in the province of CosenzaEarthquakes 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

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 ≈ 30 s

Animation sped up ~6× compared to reality.

  • Corigliano-Rossano
    28 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Cosenza
    56 km from the epicentre
    first tremor in ~9 s
    main shaking in ~16 s
  • Lamezia Terme
    91 km from the epicentre
    first tremor in ~15 s
    main shaking in ~26 s
  • Potenza
    103 km from the epicentre
    first tremor in ~17 s
    main shaking in ~30 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.

shallower than the area average (~20 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 (M2.1, 5 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.1
The mainshock
2 km South-East of Laino Borgo
5 years ago · 30 Mar 2021, 19:01
Activity in the area right now (30 km radius)
0
last 24 hours
1
last 7 days
10
last 30 days
2 before2 after
this quake
Strongest of the sequence2.1

How often does it happen here?

about every ~14 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 318 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.

11846.8
Valle del Crati earthquake
24 May 1184 · 42 km from here
IXDestructive: many buildings partly or fully collapse.
17675.9
Valle del Crati earthquake
14 July 1767 · 45 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
19135.6
Calabria settentrionale earthquake
28 June 1913 · 28 km from here
VIII-IXDestructive: many buildings partly or fully collapse.
18865.6
Cosentino earthquake
6 March 1886 · 49 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

Pollino

The epicentre lies about 3 km from Pollino, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.4between 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

1.7
5 years ago
5 May 2021, 13:21
1.4
5 years ago
4 Apr 2021, 04:53
1.3
5 km West of Morano Calabro
14 km North-West · 5 km
5 years ago
20 May 2021, 12:22
2.1
2 km South-East of Laino Borgo
27 km North-West · 19 km
5 years ago
30 Mar 2021, 19:01

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).