All earthquakes
1.6
very light
EARTHQUAKE DETAILS

M1.6 earthquake · 3 km South-West of Balvano (PZ)

11 years ago · 8 May 2015, 05:28

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

Stronger than 74% of Italian events in the past year

Where

3 km South-West of BalvanoEarthquakes in the province of PotenzaEarthquakes 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

14 events
Magnitude:lightweakmoderatestrong

The energy released

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

3.8kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×126 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 ≈ 19 s

Animation sped up ~4× compared to reality.

  • Potenza
    27 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Battipaglia
    45 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Salerno
    58 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Avellino
    66 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

10 km
medium depth
1.2 times the height of Mount Everest

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

in line with the area average (~15 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: 11 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
3 km South-East of Castelgrande
11 years ago · 5 Jun 2015, 10:56
Activity in the area right now (30 km radius)
0
last 24 hours
4
last 7 days
16
last 30 days
7 before6 after
this quake
Strongest of the sequence2.7

How often does it happen here?

about every ~13 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 339 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.
19806.8
Irpinia-Basilicata earthquake
23 November 1980 · 28 km from here
XCompletely destructive: most buildings are destroyed.
16946.7
Irpinia-Basilicata earthquake
8 September 1694 · 25 km from here
XCompletely destructive: most buildings are destroyed.
15616.7
Vallo di Diano earthquake
19 August 1561 · 9 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 sits above this source area: the deep structure where this area's earthquakes can originate.

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

1.1
4 km West of Picerno
10 km East · 11 km
11 years ago
7 May 2015, 00:41
1.2
4 km East of Muro Lucano
12 km North · 5 km
11 years ago
9 May 2015, 12:46
1.4
1 km East of Santomenna
21 km North-West · 16 km
11 years ago
27 Apr 2015, 01:44
0.9
2 km North-West of Abriola
28 km East · 19 km
11 years ago
26 Apr 2015, 16:53
1.4
11 years ago
23 May 2015, 09:01
1.1
3 km South of Sasso di Castalda
27 km South-East · 23 km
11 years ago
22 Apr 2015, 15:08
1.3
2 km South of Picerno
13 km East · 5 km
11 years ago
23 May 2015, 20:01
1.3
4 km West of Pignola
24 km East · 23 km
11 years ago
24 May 2015, 03:00
1.1
3 km North-West of Vietri di Potenza
3 km South-East · 10 km
11 years ago
17 Apr 2015, 23:56
1.2
2 km East of Muro Lucano
10 km North · 7 km
11 years ago
16 Apr 2015, 22:56

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).