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3.3
weak
EARTHQUAKE DETAILS

Costa Calabra nord-occidentale (Cosenza)

5 months ago · 6 Apr, 05:26

A weak earthquake, felt by some of the population. At this depth the shaking is felt, but rarely causes damage.

Stronger than 99% of Italian events in the past year

Where

Costa Calabra nord-occidentale (Cosenza)Earthquakes in the province of CosenzaEarthquakes in Calabria

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?

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

12 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3tof TNT equivalent
5.6 lightning bolts
M3
×2.8 the energy of a magnitude 3 earthquake
M2this quakeM4

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 ≈ 26 s

Animation sped up ~5× compared to reality.

  • Lamezia Terme
    52 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Cosenza
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Catanzaro
    81 km from the epicentre
    first tremor in ~14 s
    main shaking in ~24 s
  • Corigliano-Rossano
    89 km from the epicentre
    first tremor in ~15 s
    main shaking in ~26 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

26 km
medium depth
2.9 times the height of Mount Everest

At this depth the shaking is felt, but rarely causes damage.

shallower than the area average (~113 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: 4 months ago the same area had a stronger quake (M3.7). This can only be said after the fact — it was not predictable beforehand.

3.7
The mainshock
Tirreno Meridionale [Mare]
4 months ago · 25 Apr, 13:43
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
5
last 30 days
2 before9 after
this quake
Strongest of the sequence3.7

How often does it happen here?

about every ~41 days

Within 50 km of this epicentre, a magnitude ≥ 3 earthquake has occurred on average this often: 105 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.

19057.0
Calabria centrale earthquake
8 September 1905 · 39 km from here
X-XICatastrophic: very few buildings remain standing; landslides and ground cracks.
19285.9
Calabria centro-meridionale earthquake
7 March 1928 · 48 km from here
VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.
19945.8
Tirreno meridionale earthquake
5 January 1994 · 46 km from here
IV-VRather strong: felt by almost everyone; hanging objects swing.
20065.8
Tirreno meridionale earthquake
26 October 2006 · 43 km from here

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

The closest seismic structure

Savuto Valley

The epicentre lies about 43 km from Savuto Valley, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 2 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

1.5
Tirreno Meridionale [Mare]
20 km South-West · 11 km
5 months ago
11 Apr, 12:42
3.4
Tirreno Meridionale [Mare]
25 km North-West · 269 km
4 months ago
17 Apr, 07:16
1.6
8 km West of Longobardi
30 km East · 15 km
5 months ago
24 Mar, 21:25
1.8
7 km West of Amantea
28 km East · 13 km
5 months ago
22 Mar, 03:29
3.7
Tirreno Meridionale [Mare]
30 km North-West · 273 km
4 months ago
25 Apr, 13:43
2.0
Tirreno Meridionale [Mare]
21 km South-West · 86 km
4 months ago
25 Apr, 22:01
2.8
24 km West of San Lucido
25 km North-East · 205 km
4 months ago
27 Apr, 22:27
2.3
4 months ago
30 Apr, 00:01
2.1
19 km West of Longobardi
19 km North-East · 52 km
4 months ago
30 Apr, 16:05
2.4
Tirreno Meridionale [Mare]
19 km South · 165 km
4 months ago
2 May, 03:56

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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