All earthquakes
1.3
very light
EARTHQUAKE DETAILS

7 km South of Firenzuola

87 months ago · 27 Apr, 00:21

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 54% of Italian events in the past year

Where

7 km South of FirenzuolaEarthquakes 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

26 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×355 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 ≈ 13 s

Animation sped up ~2× compared to reality.

  • Prato
    30 km from the epicentre
    first tremor in ~5 s
    main shaking in ~9 s
  • Firenze
    34 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Pistoia
    38 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Imola
    45 km from the epicentre
    first tremor in ~8 s
    main shaking in ~13 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

8 km
shallow

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

in line with the area average (~13 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?

Aftershock

It is an aftershock: it follows a stronger quake (M2.5, 87 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.5
The mainshock
7 km South of Firenzuola
87 months ago · 20 Apr, 01:25
Activity in the area right now (30 km radius)
1
last 24 hours
7
last 7 days
22
last 30 days
12 before13 after
this quake
Strongest of the sequence2.5

How often does it happen here?

about every ~4 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 991 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 · 15 km from here
XCompletely destructive: most buildings are destroyed.
17816.1
Faentino earthquake
4 April 1781 · 40 km from here
IX-XCompletely destructive: most buildings are destroyed.
16616.0
Appennino forlivese earthquake
22 March 1661 · 43 km from here
XCompletely destructive: most buildings are destroyed.
15426.0
Mugello earthquake
13 June 1542 · 7 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 sits above this source area: the deep structure where this area's earthquakes can originate.

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

1.0
6 km South of Firenzuola
1 km North-East · 8 km
87 months ago
27 Apr, 12:19
2.4
6 km South of Firenzuola
1 km North · 7 km
87 months ago
26 Apr, 07:49
1.4
5 km East of Casola Valsenio
28 km North-East · 23 km
87 months ago
26 Apr, 06:32
0.9
9 km South of Firenzuola
1 km South · 12 km
87 months ago
23 Apr, 13:49
1.1
4 km West of Vernio
21 km West · 11 km
87 months ago
22 Apr, 19:20
1.1
7 km South of Firenzuola
1 km North · 8 km
87 months ago
21 Apr, 00:00
1.3
7 km South of Firenzuola
1 km North-East · 8 km
87 months ago
20 Apr, 22:32
2.5
7 km South of Firenzuola
1 km North-West · 8 km
87 months ago
20 Apr, 01:25
1.1
86 months ago
7 May, 19:39
1.1
86 months ago
7 May, 19:41

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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