All earthquakes
0.7
very light
EARTHQUAKE DETAILS

M0.7 earthquake · 5 km East of Montella (AV)

5 years ago · 28 Jul 2021, 23:45

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 11% of Italian events in the past year

Where

5 km East of MontellaEarthquakes in the province of AvellinoEarthquakes in Campania

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

11 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.2kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×2,818 its energy
M0this quakeM2

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 ≈ 10 s

Animation sped up ~2× compared to reality.

  • Avellino
    24 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Battipaglia
    29 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Salerno
    29 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Cava de' Tirreni
    34 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 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

9 km
shallow
1 times the height of Mount Everest

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

in line with the area average (~14 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: 5 years ago the same area had a stronger quake (M1.7). This can only be said after the fact — it was not predictable beforehand.

1.7
The mainshock
1 km North-East of Trevico
5 years ago · 1 Aug 2021, 22:01
Activity in the area right now (30 km radius)
0
last 24 hours
5
last 7 days
12
last 30 days
3 before7 after
this quake
Strongest of the sequence1.7

How often does it happen here?

about every ~11 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 400 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.

19806.8
Irpinia-Basilicata earthquake
23 November 1980 · 19 km from here
XCompletely destructive: most buildings are destroyed.
17326.8
Irpinia earthquake
29 November 1732 · 24 km from here
X-XICatastrophic: very few buildings remain standing; landslides and ground cracks.
16946.7
Irpinia-Basilicata earthquake
8 September 1694 · 29 km from here
XCompletely destructive: most buildings are destroyed.
15616.7
Vallo di Diano earthquake
19 August 1561 · 49 km from here
X-XICatastrophic: very few buildings remain standing; landslides and ground cracks.

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

The closest seismic structure

Irpinia-Agri Valley

The epicentre lies about 6 km from Irpinia-Agri Valley, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.8between 1 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

1.0
4 km North-East of Senerchia
19 km East · 10 km
5 years ago
29 Jul 2021, 00:11
1.2
3 km North-West of Caposele
12 km East · 11 km
5 years ago
30 Jul 2021, 23:10
1.7
1 km North-East of Trevico
29 km North-East · 16 km
5 years ago
1 Aug 2021, 22:01
1.7
3 km East of Palomonte
30 km South-East · 11 km
5 years ago
8 Aug 2021, 13:21
0.9
5 years ago
13 Aug 2021, 19:02
1.3
2 km North-East of Colliano
27 km South-East · 8 km
5 years ago
7 Jul 2021, 16:11
1.4
1 km North-East of Colliano
26 km South-East · 7 km
5 years ago
7 Jul 2021, 15:50
1.1
1 km West of Santomenna
24 km East · 7 km
5 years ago
21 Aug 2021, 23:26
1.6
2 km North-East of Trevico
30 km North-East · 14 km
5 years ago
2 Jul 2021, 22:04
1.7
3 km South-West of Colliano
26 km South-East · 5 km
5 years ago
26 Aug 2021, 21:22

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).