All earthquakes
1.9
very light
EARTHQUAKE DETAILS

M1.9 earthquake · 1 km North-West of Poggio Imperiale (FG)

10 years ago · 4 May 2016, 05:36

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 85% of Italian events in the past year

Where

1 km North-West of Poggio ImperialeEarthquakes in the province of FoggiaEarthquakes in Puglia

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

8 events
Magnitude:lightweakmoderatestrong

The energy released

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

11kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×45 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 ≈ 22 s

Animation sped up ~4× compared to reality.

  • San Severo
    28 km from the epicentre
    first tremor in ~5 s
    main shaking in ~8 s
  • Manfredonia
    46 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Foggia
    47 km from the epicentre
    first tremor in ~8 s
    main shaking in ~14 s
  • Cerignola
    75 km from the epicentre
    first tremor in ~13 s
    main shaking in ~22 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

7 km
shallow

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

shallower than the area average (~16 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: 10 years ago the same area had a stronger quake (M2.9). This can only be said after the fact — it was not predictable beforehand.

2.9
The mainshock
1 km North of Casalvecchio di Puglia
10 years ago · 31 May 2016, 13:34
Activity in the area right now (30 km radius)
0
last 24 hours
2
last 7 days
8
last 30 days
3 before4 after
this quake
Strongest of the sequence2.9

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: 634 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.

16276.7
Capitanata earthquake
30 July 1627 · 11 km from here
XCompletely destructive: most buildings are destroyed.
16276.0
Capitanata earthquake
7 August 1627 · 10 km from here
IXDestructive: many buildings partly or fully collapse.
16576.0
Capitanata earthquake
29 January 1657 · 12 km from here
IX-XCompletely destructive: most buildings are destroyed.
18755.9
Gargano earthquake
6 December 1875 · 30 km from here
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

Ripabottoni-San Severo

The epicentre lies about 12 km from Ripabottoni-San Severo, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 7.1between 6 and 25 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
9 km North of Lesina
13 km North · 10 km
10 years ago
6 May 2016, 01:33
2.4
10 years ago
1 May 2016, 12:45
1.6
10 years ago
18 Apr 2016, 11:44
2.4
10 years ago
25 May 2016, 21:20
1.7
7 km North of Lesina
11 km North · 9 km
10 years ago
26 May 2016, 23:30
1.5
10 years ago
8 Apr 2016, 23:08
2.9
1 km North of Casalvecchio di Puglia
30 km South-West · 21 km
10 years ago
31 May 2016, 13:34

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).