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2.7
light
EARTHQUAKE DETAILS

M2.7 earthquake outside Italy

6 years ago · 11 Jul 2020, 13:53

A light earthquake, rarely felt by people. At this depth the shaking is felt, but rarely causes damage.

The strongest of the past 12 months within 50 km

Where

Nearest Italian town: Curiglia con Monteviasco (VA)Earthquakes in the province of VareseEarthquakes 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

2 events
Magnitude:lightweakmoderatestrong

The energy released

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

169kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×2.8 its energy
M2this quakeM4

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 ≈ 20 s

Animation sped up ~4× compared to reality.

  • Varese
    44 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 s
  • Como
    50 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Gallarate
    63 km from the epicentre
    first tremor in ~11 s
    main shaking in ~18 s
  • Busto Arsizio
    69 km from the epicentre
    first tremor in ~12 s
    main shaking in ~20 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

12 km
medium depth
1.3 times the height of Mount Everest

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

in line with the area average (~11 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?

Isolated quake

In the 30 days around this event no other quakes were recorded within 30 km: a one-off episode, very common in Italy.

Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
1 before0 after
this quake
Strongest of the sequence1.5

How often does it happen here?

about every ~2.9 years

Within 50 km of this epicentre, a magnitude ≥ 2.5 earthquake has occurred on average this often: 4 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.

15124.6
Valchiavenna earthquake
8 February 1512 · 42 km from here
VIStrong: felt by everyone, many get scared; objects fall, first light damage to buildings.
19514.3
Vallemaggia, Cevio earthquake
16 May 1951 · 24 km from here
19234.3
Ticino, Bellinzona earthquake
9 November 1923 · 10 km from here
18914.0
Val d'Ossola earthquake
20 December 1891 · 45 km from here
VRather strong: felt by almost everyone; hanging objects swing.

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 65 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

1.5
6 years ago
25 Jun 2020, 08:02

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).