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EARTHQUAKE DETAILS

Tirreno Centrale [Mare]

85 months ago · 21 Aug, 20:04

A weak earthquake, felt by some of the population. At this depth the shaking is felt, but rarely causes damage.

Stronger than 99% of Italian events in the past yearNo. 1 of the year in Lazio

Where

Tirreno Centrale [Mare]Earthquakes in the province of RomaEarthquakes in Lazio

Epicentre at sea

The epicentre is at sea: for the same magnitude, the shaking is felt less on land, because the energy fades along the way before reaching the coast.

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

1 events
Magnitude:lightweakmoderatestrong

The energy released

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

1.3tof TNT equivalent
5.6 lightning bolts
M3
×2.8 the energy of a magnitude 3 earthquake
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 ≈ 21 s

Animation sped up ~4× compared to reality.

  • Fiumicino
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Civitavecchia
    55 km from the epicentre
    first tremor in ~10 s
    main shaking in ~17 s
  • Roma
    59 km from the epicentre
    first tremor in ~11 s
    main shaking in ~18 s
  • Pomezia
    71 km from the epicentre
    first tremor in ~12 s
    main shaking in ~21 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

21 km
medium depth
2.4 times the height of Mount Everest

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

in line with the area average (~16 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

No other quakes within 30 km in the 30 days around the event.

How often does it happen here?

It is the first magnitude ≥ 3 earthquake recorded within 50 km since 2014, the start of our archive.

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.

19694.5
Monti della Tolfa earthquake
2 July 1969 · 44 km from here

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

The closest seismic structure

Castelli Romani

The epicentre lies about 78 km from Castelli Romani, one of the seismic structures mapped by INGV geologists.

estimated maximum magnitude 5.9between 5 and 11 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).

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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