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0.5
very light
EARTHQUAKE DETAILS

4 km South-East of Acqualagna

71 months ago · 12 Aug, 09:21

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

Stronger than 3% of Italian events in the past year

Where

4 km South-East of AcqualagnaEarthquakes in the province of Pesaro e UrbinoEarthquakes in Marche

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

61 events
Magnitude:lightweakmoderatestrong

The energy released

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

0.1kgof TNT equivalent
Less than the energy of a lightning bolt
M3
A magnitude 3 earthquake releases ×5,623 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 ≈ 18 s

Animation sped up ~3× compared to reality.

  • Pesaro
    31 km from the epicentre
    first tremor in ~6 s
    main shaking in ~10 s
  • Fano
    33 km from the epicentre
    first tremor in ~6 s
    main shaking in ~11 s
  • Rimini
    49 km from the epicentre
    first tremor in ~9 s
    main shaking in ~15 s
  • Perugia
    61 km from the epicentre
    first tremor in ~11 s
    main shaking in ~18 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

18 km
medium depth
2 times the height of Mount Everest

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

deeper than 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: 70 months ago the same area had a stronger quake (M2.9). This can only be said after the fact — it was not predictable beforehand.

2.9
The mainshock
3 km South-West of Cantiano
70 months ago · 2 Sept, 10:38
Activity in the area right now (30 km radius)
1
last 24 hours
20
last 7 days
115
last 30 days
74 before95 after
this quake
Strongest of the sequence2.9

How often does it happen here?

about every ~7 days

Within 50 km of this epicentre, a magnitude ≥ 2 earthquake has occurred on average this often: 571 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.

17816.5
Cagliese earthquake
3 June 1781 · 14 km from here
XCompletely destructive: most buildings are destroyed.
17516.4
Appennino umbro-marchigiano earthquake
27 July 1751 · 43 km from here
XCompletely destructive: most buildings are destroyed.
13526.3
Alta Valtiberina earthquake
25 December 1352 · 47 km from here
IXDestructive: many buildings partly or fully collapse.
17416.2
Fabrianese earthquake
24 April 1741 · 33 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

Urbino-Camerino

The epicentre sits above this source area: the deep structure where this area's earthquakes can originate.

estimated maximum magnitude 6.9between 3 and 9 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

0.9
4 km South-East of Pietralunga
28 km South-West · 5 km
71 months ago
12 Aug, 11:43
0.3
5 km North-East of Pietralunga
24 km South-West · 6 km
71 months ago
12 Aug, 06:20
0.7
5 km East of Pietralunga
24 km South-West · 9 km
71 months ago
12 Aug, 03:56
1.2
6 km East of Pietralunga
26 km South-West · 9 km
71 months ago
12 Aug, 17:33
0.6
9 km North of Gubbio
26 km South-West · 8 km
71 months ago
13 Aug, 02:09
0.5
9 km North of Gubbio
26 km South-West · 10 km
71 months ago
11 Aug, 14:36
0.4
7 km South-East of Pietralunga
28 km South-West · 6 km
71 months ago
11 Aug, 13:25
0.7
6 km South-West of Cagli
11 km South-West · 11 km
71 months ago
11 Aug, 09:28
1.4
7 km South-East of Pietralunga
27 km South-West · 9 km
71 months ago
13 Aug, 20:49
0.2
8 km South-East of Pietralunga
28 km South-West · 7 km
71 months ago
14 Aug, 04:43

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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