All earthquakes
1.2
very light
EARTHQUAKE DETAILS

M1.2 earthquake outside Italy

8 years ago · 1 Dec 2017, 14:55

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

Where

Nearest Italian town: Lanzada (SO)Earthquakes in the province of SondrioEarthquakes in Lombardia

Epicentre abroad

The epicentre lies outside Italy's borders. The quake appears here because the INGV seismic network also records events close to Italy, which can be felt on Italian territory.

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

6 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.0kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×501 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 ≈ 31 s

Animation sped up ~6× compared to reality.

  • Bergamo
    87 km from the epicentre
    first tremor in ~15 s
    main shaking in ~25 s
  • Como
    93 km from the epicentre
    first tremor in ~16 s
    main shaking in ~27 s
  • Varese
    105 km from the epicentre
    first tremor in ~18 s
    main shaking in ~30 s
  • Monza
    106 km from the epicentre
    first tremor in ~18 s
    main shaking in ~31 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

15 km
medium depth
1.6 times the height of Mount Everest

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

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?

Mainshock

It is the strongest quake of its sequence: so far it has been followed by 2 aftershocks within 30 km. Aftershocks tend to fade in number and strength over time.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
1
last 30 days
3 before2 after
this quake
Strongest of the sequence1.2

How often does it happen here?

about every ~4 months

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 34 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.

12956.2
Grigioni, Churwalden earthquake
3 September 1295 · 41 km from here
18275.0
Bassa Engadina, Ardez earthquake
2 April 1827 · 35 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
16955.0
Grigioni, Region Praettigau earthquake
11 September 1695 · 47 km from here
19994.8
Alpi Retiche earthquake
29 December 1999 · 39 km from here
V-VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.

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

The closest seismic structure

Western S-Alps internal thrust

The epicentre lies about 84 km from Western S-Alps internal thrust, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.9between 5 and 12 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
Confine Italia-Svizzera (SVIZZERA)
26 km North-West · 9 km
8 years ago
30 Nov 2017, 10:22
1.0
Confine Italia-Svizzera (SVIZZERA)
26 km North-West · 10 km
8 years ago
30 Nov 2017, 10:17
0.6
22 km West of Livigno
11 km North · 10 km
8 years ago
4 Dec 2017, 03:04
1.0
9 km West of Grosio
27 km East · 10 km
8 years ago
4 Nov 2017, 08:39
1.0
5 km East of Lanzada
20 km South-East · 12 km
8 years ago
31 Dec 2017, 14:28

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).