All earthquakes
3.5
weak
EARTHQUAKE DETAILS

4 km South-West of Valfornace

116 months ago · 4 Dec, 21:22

A weak earthquake, felt by some of the population. At only a few km deep the shaking is felt more sharply at the surface.

Stronger than 99% of Italian events in the past yearNo. 4 of the year in Marche

Where

4 km South-West of ValfornaceEarthquakes in the province of MacerataEarthquakes in Marche

How far away could it be felt?

An estimate of how far people may have felt this quake.

  • up to ~5 km · felt by many people, especially on upper floors
    ≈ 1,000 people live in this area
  • up to ~24 km · felt only by some, at rest
    ≈ 43,000 people live in this area

The coloured rings on the map below show these distances.

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

61 events
Magnitude:lightweakmoderatestrong

The energy released

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

2.7tof TNT equivalent
11 lightning bolts
M3
×5.6 the energy of a magnitude 3 earthquake
M3this quakeM5

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 ≈ 19 s

Animation sped up ~3× compared to reality.

  • Foligno
    25 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Perugia
    61 km from the epicentre
    first tremor in ~10 s
    main shaking in ~18 s
  • Terni
    62 km from the epicentre
    first tremor in ~11 s
    main shaking in ~18 s
  • Teramo
    65 km from the epicentre
    first tremor in ~11 s
    main shaking in ~19 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

8 km
shallow

At only a few km deep the shaking is felt more sharply at the surface.

in line with the area average (~11 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?

Isolated quake

In the 30 days around this event no other quakes were recorded within 30 km: a one-off episode, very common in Italy.

Activity in the area right now (30 km radius)
7
last 24 hours
56
last 7 days
316
last 30 days
0 before2000 after
this quake
Strongest of the sequence3.5

How often does it happen here?

about every ~15 days

Within 50 km of this epicentre, a magnitude ≥ 3.5 earthquake has occurred on average this often: 288 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.

17036.9
Valnerina earthquake
14 January 1703 · 37 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
20166.6
Valnerina earthquake
30 October 2016 · 24 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
13286.5
Valnerina earthquake
1 December 1328 · 22 km from here
XCompletely destructive: most buildings are destroyed.
18326.4
Valle Umbra earthquake
13 January 1832 · 41 km from here
XCompletely destructive: most buildings are destroyed.

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

The closest seismic structure

Muccia-Castelluccio di Norcia

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

estimated maximum magnitude 6.9between 2 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

1.3
4 km North-East of Norcia
28 km South · 19 km
115 months ago
25 Dec, 22:53
2.3
115 months ago
25 Dec, 23:02
2.0
115 months ago
25 Dec, 23:03
1.9
115 months ago
25 Dec, 23:03
1.4
5 km East of Muccia
3 km North-West · 9 km
115 months ago
25 Dec, 23:05
1.4
115 months ago
25 Dec, 23:06
1.5
115 months ago
25 Dec, 23:07
2.4
5 km South-East of Muccia
2 km West · 9 km
115 months ago
25 Dec, 23:12
1.3
4 km East of Ussita
15 km South-East · 6 km
115 months ago
25 Dec, 23:18
1.4
4 km North of Norcia
26 km South · 9 km
115 months ago
25 Dec, 23:30

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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