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EARTHQUAKE DETAILS

Mar Ionio Settentrionale [Mare]

8 months ago · 18 Dec, 13:44

A light earthquake, rarely felt by people. Being deep, it is felt less at the surface.

Stronger than 92% of Italian events in the past year

Where

Mar Ionio Settentrionale [Mare]Earthquakes in the province of Reggio CalabriaEarthquakes 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

2 events
Magnitude:lightweakmoderatestrong

The energy released

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

30kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×16 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 ≈ 39 s

Animation sped up ~7× compared to reality.

  • Reggio di Calabria
    84 km from the epicentre
    first tremor in ~15 s
    main shaking in ~26 s
  • Messina
    104 km from the epicentre
    first tremor in ~19 s
    main shaking in ~32 s
  • Acireale
    118 km from the epicentre
    first tremor in ~21 s
    main shaking in ~35 s
  • Catania
    131 km from the epicentre
    first tremor in ~23 s
    main shaking in ~39 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

38 km
deep
4.3 times the height of Mount Everest

Being deep, it is felt less at the surface.

deeper than the area average (~31 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: 8 months ago the same area had a stronger quake (M5.1). This can only be said after the fact — it was not predictable beforehand.

5.1
The mainshock
Costa Calabra sud-orientale (Reggio di Calabria)
8 months ago · 10 Jan, 05:53
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
0 before1 after
this quake
Strongest of the sequence5.1

How often does it happen here?

about every ~20 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 208 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.

18975.0
Ionio meridionale earthquake
11 February 1897 · 50 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
20124.6
Ionio meridionale earthquake
4 July 2012 · 33 km from here
20134.6
Ionio meridionale earthquake
24 March 2013 · 23 km from here
20014.5
Ionio meridionale earthquake
26 May 2001 · 34 km from here
III-IVModerate: felt by many indoors; glasses and dishes rattle.

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

The closest seismic structure

Calabria offshore SW

The epicentre lies about 31 km from Calabria offshore SW, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.9between 4 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

5.1
8 months ago
10 Jan, 05:53

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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