All earthquakes
1.7
very light
EARTHQUAKE DETAILS

5 km East of Pietralunga

99 months ago · 20 Apr, 11:37

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 78% of Italian events in the past year

Where

5 km East of PietralungaEarthquakes in the province of PerugiaEarthquakes in Umbria

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

61 events
Magnitude:lightweakmoderatestrong

The energy released

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

5.4kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×89 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 ≈ 16 s

Animation sped up ~3× compared to reality.

  • Perugia
    36 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Arezzo
    44 km from the epicentre
    first tremor in ~7 s
    main shaking in ~13 s
  • Pesaro
    57 km from the epicentre
    first tremor in ~10 s
    main shaking in ~16 s
  • Foligno
    57 km from the epicentre
    first tremor in ~10 s
    main shaking in ~16 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 (~10 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, 100 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.1
The mainshock
4 km East of Pietralunga
100 months ago · 3 Apr, 14:42
Activity in the area right now (30 km radius)
3
last 24 hours
31
last 7 days
165
last 30 days
45 before65 after
this quake
Strongest of the sequence2.1

How often does it happen here?

about every ~7 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 586 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.

17816.5
Cagliese earthquake
3 June 1781 · 19 km from here
XCompletely destructive: most buildings are destroyed.
17516.4
Appennino umbro-marchigiano earthquake
27 July 1751 · 32 km from here
XCompletely destructive: most buildings are destroyed.
13526.3
Alta Valtiberina earthquake
25 December 1352 · 27 km from here
IXDestructive: many buildings partly or fully collapse.
17416.2
Fabrianese earthquake
24 April 1741 · 44 km from here
IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Gubbio Basin

The epicentre lies about 2 km from Gubbio Basin, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.0between 2 and 7 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

1.2
4 km South of Frontone
21 km East · 14 km
99 months ago
20 Apr, 12:56
1.0
3 km North of Pietralunga
6 km North-West · 6 km
99 months ago
20 Apr, 18:07
0.3
5 km East of Pietralunga
4 km North · 11 km
99 months ago
20 Apr, 01:39
1.9
8 km East of Pietralunga
4 km East · 9 km
99 months ago
20 Apr, 22:32
2.0
99 months ago
20 Apr, 22:56
1.9
99 months ago
21 Apr, 06:43
1.0
99 months ago
19 Apr, 15:33
1.5
8 km North-East of Pietralunga
6 km North-East · 11 km
99 months ago
19 Apr, 15:16
1.7
7 km North-East of Pietralunga
6 km North-East · 9 km
99 months ago
19 Apr, 15:09
1.2
4 km North-West of Valfabbrica
27 km South-East · 9 km
99 months ago
21 Apr, 09:01

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).

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