All earthquakes
1.2
very light
EARTHQUAKE DETAILS

4 km East of Rocca San Casciano

38 months ago · 27 Apr, 05:00

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

Stronger than 47% of Italian events in the past year

Where

4 km East of Rocca San CascianoEarthquakes in the province of Forlì-CesenaEarthquakes in Emilia-Romagna

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

32 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.

  • Forlì
    21 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Cesena
    26 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Faenza
    27 km from the epicentre
    first tremor in ~7 s
    main shaking in ~11 s
  • Imola
    40 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

28 km
medium depth
3.2 times the height of Mount Everest

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

deeper than 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 (M2.7, 38 months ago) in the same area. Aftershocks are normal after an earthquake and tend to fade over time.

2.7
The mainshock
4 km South of Rocca San Casciano
38 months ago · 23 Apr, 18:17
Activity in the area right now (30 km radius)
0
last 24 hours
4
last 7 days
11
last 30 days
22 before9 after
this quake
Strongest of the sequence2.7

How often does it happen here?

about every ~6 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 752 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.

19196.4
Mugello earthquake
29 June 1919 · 35 km from here
XCompletely destructive: most buildings are destroyed.
17816.1
Faentino earthquake
4 April 1781 · 23 km from here
IX-XCompletely destructive: most buildings are destroyed.
16616.0
Appennino forlivese earthquake
22 March 1661 · 4 km from here
XCompletely destructive: most buildings are destroyed.
15426.0
Mugello earthquake
13 June 1542 · 41 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

Castel San Pietro Terme-Meldola

The epicentre lies about 11 km from Castel San Pietro Terme-Meldola, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 6.5between 2 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

1.8
38 months ago
23 Apr, 18:33
1.6
38 months ago
23 Apr, 18:23
1.5
5 km North of Galeata
3 km East · 29 km
38 months ago
23 Apr, 18:22
2.0
38 months ago
23 Apr, 18:20
1.8
38 months ago
23 Apr, 18:19
2.7
38 months ago
23 Apr, 18:17
1.2
38 months ago
23 Apr, 18:06
0.4
5 km East of Casola Valsenio
24 km North-West · 19 km
38 months ago
30 Apr, 19:10
0.9
4 km North of Bagno di Romagna
17 km South-East · 15 km
38 months ago
20 Apr, 15:44
1.2
3 km North of Bagno di Romagna
17 km South · 15 km
38 months ago
20 Apr, 09:45

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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