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2.6
light
EARTHQUAKE DETAILS

M2.6 offshore earthquake

3 years ago · 22 Dec 2022, 20:56

A light earthquake, rarely felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 96% of Italian events in the past year

Where

Nearest Italian town: Ponza (LT)Earthquakes in the province of LatinaEarthquakes in Lazio

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

4 events
Magnitude:lightweakmoderatestrong

The energy released

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

120kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×4 its energy
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 ≈ 31 s

Animation sped up ~6× compared to reality.

  • Latina
    85 km from the epicentre
    first tremor in ~15 s
    main shaking in ~25 s
  • Aprilia
    100 km from the epicentre
    first tremor in ~17 s
    main shaking in ~29 s
  • Velletri
    106 km from the epicentre
    first tremor in ~18 s
    main shaking in ~31 s
  • Pozzuoli
    108 km from the epicentre
    first tremor in ~18 s
    main shaking in ~31 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

20 km
medium depth
2.3 times the height of Mount Everest

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

deeper than the area average (~13 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 (M2.8, 3 years ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.8
The mainshock
20 km South of Ponza
3 years ago · 22 Dec 2022, 20:53
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
1 before2 after
this quake
Strongest of the sequence2.8

How often does it happen here?

about every ~13 months

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 11 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.

17934.6
Isole Pontine earthquake
25 July 1793 · 34 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19074.4
Isola di Ponza earthquake
3 March 1907 · 24 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18924.4
Isola di Ponza earthquake
16 November 1892 · 25 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
19894.2
Tirreno centrale earthquake
3 July 1989 · 20 km from here

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

The closest seismic structure

Ischia

The epicentre lies about 84 km from Ischia, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 5.4between 0 and 4 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

2.8
20 km South of Ponza
7 km North-East · 21 km
3 years ago
22 Dec 2022, 20:53
1.8
17 km South of Ponza
9 km North-East · 21 km
3 years ago
22 Dec 2022, 21:59
2.2
Tirreno Centrale [Mare]
5 km South-West · 28 km
3 years ago
26 Dec 2022, 13:01

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).