All earthquakes
1.2
very light
EARTHQUAKE DETAILS

5 km South-East of Montelupo Fiorentino

128 months ago · 24 Dec, 04:31

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 47% of Italian events in the past year

Where

5 km South-East of Montelupo FiorentinoEarthquakes in the province of FirenzeEarthquakes in Toscana

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

7 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 ≈ 14 s

Animation sped up ~3× compared to reality.

  • Firenze
    18 km from the epicentre
    first tremor in ~3 s
    main shaking in ~6 s
  • Prato
    21 km from the epicentre
    first tremor in ~4 s
    main shaking in ~7 s
  • Pistoia
    36 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Siena
    49 km from the epicentre
    first tremor in ~8 s
    main shaking in ~14 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

9 km
shallow
1 times the height of Mount Everest

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

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?

Foreshock

In hindsight it was a foreshock: 127 months ago the same area had a stronger quake (M2.4). This can only be said after the fact — it was not predictable beforehand.

2.4
The mainshock
5 km South-West of San Casciano in Val di Pesa
127 months ago · 26 Dec, 09:59
Activity in the area right now (30 km radius)
0
last 24 hours
0
last 7 days
0
last 30 days
2 before4 after
this quake
Strongest of the sequence2.4

How often does it happen here?

about every ~10 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 439 events in the last 11 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.

19196.4
Mugello earthquake
29 June 1919 · 45 km from here
XCompletely destructive: most buildings are destroyed.
18466.0
Colline Pisane earthquake
14 August 1846 · 47 km from here
XCompletely destructive: most buildings are destroyed.
15426.0
Mugello earthquake
13 June 1542 · 43 km from here
IXDestructive: many buildings partly or fully collapse.
15586.0
Valdarno superiore earthquake
13 April 1558 · 49 km from here
IXDestructive: many buildings partly or fully collapse.

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

The closest seismic structure

Mugello-Citta' di Castello-Leonessa

The epicentre lies about 36 km from Mugello-Citta' di Castello-Leonessa, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.9between 1 and 8 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

2.4
127 months ago
26 Dec, 09:59
1.7
127 months ago
26 Dec, 10:29
1.3
1 km West of Larciano
23 km North-West · 5 km
128 months ago
28 Nov, 05:24
1.4
3 km West of Signa
10 km North · 7 km
127 months ago
21 Jan, 18:14
0.8
127 months ago
21 Jan, 18:17
0.6
128 months ago
25 Nov, 03:15

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).

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