All earthquakes
1.8
very light
EARTHQUAKE DETAILS

M1.8 earthquake · 4 km North-East of Stigliano (MT)

6 years ago · 21 Jul 2020, 00:31

A very light earthquake, probably not felt by people. At this depth the shaking is felt, but rarely causes damage.

Stronger than 82% of Italian events in the past year

Where

4 km North-East of StiglianoEarthquakes in the province of MateraEarthquakes in Basilicata

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

12 events
Magnitude:lightweakmoderatestrong

The energy released

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

7.6kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×63 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 ≈ 23 s

Animation sped up ~4× compared to reality.

  • Matera
    43 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Altamura
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Potenza
    57 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Bitonto
    79 km from the epicentre
    first tremor in ~14 s
    main shaking in ~23 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

18 km
medium depth
2 times the height of Mount Everest

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

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: 6 years ago the same area had a stronger quake (M2.7). This can only be said after the fact — it was not predictable beforehand.

2.7
The mainshock
5 km North-West of Bernalda
6 years ago · 22 Jul 2020, 02:14
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
3
last 30 days
5 before6 after
this quake
Strongest of the sequence2.7

How often does it happen here?

about every ~23 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 189 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.

18577.1
Basilicata earthquake
16 December 1857 · 44 km from here
XICatastrophic: very few buildings remain standing; landslides and ground cracks.
19985.5
Appennino lucano earthquake
9 September 1998 · 49 km from here
VIIVery strong: hard to stand; chimneys and roof tiles fall, serious damage to weaker buildings.
19175.5
Val d'Agri earthquake
13 October 1917 · 34 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
18575.3
Basilicata earthquake
26 December 1857 · 32 km from here
VII-VIIIRuinous: partial collapses in ordinary buildings, widespread heavy damage.

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

The closest seismic structure

Baragiano-Palagianello

The epicentre lies about 31 km from Baragiano-Palagianello, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.4between 13 and 22 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

1.8
3 km East of Stigliano
0 km South · 19 km
6 years ago
21 Jul 2020, 00:34
2.7
5 km North-West of Bernalda
30 km East · 7 km
6 years ago
22 Jul 2020, 02:14
1.6
3 km South of Montescaglioso
28 km East · 10 km
6 years ago
22 Jul 2020, 02:15
1.4
5 km South-West of Ferrandina
8 km North-East · 14 km
6 years ago
9 Jul 2020, 20:38
1.7
5 km North-East of Stigliano
1 km North-East · 23 km
6 years ago
6 Jul 2020, 22:22
2.0
5 km North-East of Stigliano
2 km North · 20 km
6 years ago
6 Jul 2020, 22:18
1.8
4 km South-West of San Mauro Forte
10 km North-West · 15 km
6 years ago
5 Jul 2020, 22:33
2.7
6 years ago
5 Aug 2020, 07:24
1.4
8 km North-East of Salandra
22 km North · 10 km
6 years ago
7 Aug 2020, 15:07
1.5
8 km East of Salandra
22 km North · 11 km
6 years ago
7 Aug 2020, 18:37

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).