Earthquake with magnitude of ML 0.8 on date 28-10-2021 and time 02:31:04 (UTC) in region 4 km W Montieri (GR)

A magnitude ML 0.8 earthquake occured in region: 4 km W Montieri (GR), on

  • 28-10-2021 02:31:04 (UTC)
  • 28-10-2021 04:31:04 (UTC +02:00) Italian time

and geographic coordinates (lat, lon) 43.145, 10.969 at 9 km depth.

The earthquake was located by: Sala Sismica INGV-Roma.

Search earthquakes: Any within 30 km radius

The values of hypocentral coordinates and magnitude may be revised at a later time as more information becomes available.

Municipalities within 20 km from the epicenter

Distances are determinated based on the geographic coordintes of the (Istat).
Municipality Region Dist Inh Cum Inh
Montieri GR 4 1204 1204
Castelnuovo di Val di Cecina PI 9 2231 3435
Monterotondo Marittimo GR 9 1371 4806
Chiusdino SI 10 1903 6709
Massa Marittima GR 12 8375 15084
Radicondoli SI 14 914 15998
Monticiano SI 17 1571 17569
Pomarance PI 19 5897 23466

Municipalities with at least 50000 inhabitants

An earthquake occurred to
35 Km SW of Siena (53903 inhabitants)
44 Km N of Grosseto (82087 inhabitants)
70 Km SE of Livorno (159219 inhabitants)
71 Km S of Scandicci (50609 inhabitants)
73 Km SW of Firenze (382808 inhabitants)
78 Km SE of Pisa (89158 inhabitants)
82 Km W of Arezzo (99543 inhabitants)
83 Km S of Prato (191150 inhabitants)
87 Km SE of Lucca (89046 inhabitants)
88 Km S of Pistoia (90315 inhabitants)
99 Km SE of Viareggio (62467 inhabitants)
Recent and historical seismicity
Seismic hazard
Felt maps
Preliminary map of the earthquake effects from the web questionnaire

Preliminary map of the earthquake effects from the web questionnaire

This map shows the distribution of earthquake resentment in the area, expressed in terms of intensity on the MCS scale (Mercalli-Cancani-Sieberg). Intensities are determined using data from questionnaires collected on the website The intensities shown are determined considering all the reports received from each municipality, and are all the more reliable the greater the number of questionnaires. The collected data are subjected to an automatic statistical filter, but are not checked individually. In particular, intensities greater than or equal to the VI degree of the MCS or EMS scale require on-site verification by specialized personnel. The black star is the epicenter of the earthquake that occurred. This map is updated every time citizens fill out new questionnaires. The number of questionnaires processed to obtain this map, the date and time of the last update are shown at the top right.
Locations history
Type Magnitude Date and Time (UTC) Latitude Longitude Depth (km) Published time (UTC) Author Location ID
ML 0.8 2021-10-28
43.1447 10.9693 9 2021-10-28
Sala Sismica INGV-Roma 97031731
Preferred location and magnitude until now.
Origin information


Field Value
Time (UTC) 2021-10-28 02:31:04 ± 0.28
Latitude 43.1447 ± 0.0135
Longitude 10.9693 ± 0.0197
Depth (km) 9 ± 1 (from location)
Evaluation mode of Origin manual
Evaluation status of Origin reviewed
Version 100 -> SURVEY-INGV
Event type earthquake
Origin ID 97031731


Field Value
Preferred uncertainty description uncertainty ellipse
Semi-major axis of confidence ellipse (meter) 1690
Semi-minor axis of confidence ellipse (meter) 1151
Azimuth of major axis of confidence ellipse. Measured clockwise from South-North direction at epicenter (gradi) 313
Circular confidence region, given by single value of horizontal uncertainty (meter) 1690
Confidence level of the uncertainty (%) 68


Field Value
Largest azimuthal gap in station distribution as seen from epicenter (degree) 185
Number of associated phases, regardless of their use for origin computation 7
Number of defining phases 7
RMS of the travel time residuals of the arrivals used for the origin computation (sec) 0.34
Epicentral distance of station closest to the epicenter (degree) 0.05666
Epicentral distance of station farthest from the epicenter (degree) 0.36153
Number of stations at which the event was observed 4
Number of stations from which data was used for origin computation 4
Magnitude information


Field Value
Value 0.8
Uncertainty 0
Num. used stations 2
Type of magnitude ML
Reference to an origin 97031731
Agency INGV
Autore Sala Sismica INGV-Roma
Time of creation (UTC) 2021-10-28 02:57:13
Picking and Arrival
SCNL Time Uncertainty Polarity Evaluation_mode Phase Azimuth Distance Takeoff_angle Residual Weight
IV.CASP.HHZ. 2021-10-28T02:31:17.93 0.6 undecidable manual S 192 0.3615 50 -0.5 44
IV.RIBO.EHZ.01 2021-10-28T02:31:13.16 0.6 undecidable manual S 164 0.2032 112 -0.05 50
IV.CASP.HHZ. 2021-10-28T02:31:13.13 0.6 negative manual P 192 0.3615 50 0.47 44
IV.RIBO.EHZ.01 2021-10-28T02:31:09.87 0.3 undecidable manual P 164 0.2032 112 0.22 72
IV.TRIF.CHZ. 2021-10-28T02:31:08.23 0.6 undecidable manual S 239 0.0567 145 -0.35 48
IV.FROS.CHZ. 2021-10-28T02:31:08.44 0.1 positive manual P 64 0.1511 118 -0.14 99
IV.TRIF.CHZ. 2021-10-28T02:31:07.16 0.1 undecidable manual P 239 0.0567 145 0.19 100
Station Magnitude and Amplitude
SCNL mag Generic_amplitude Period Type Category Unit Time_window_reference
IV.TRIF.CHN. ML:0.8 0.0001035 0.08 AML other m 2021-10-28T02:31:08.51
IV.TRIF.CHE. ML:0.8 9.99E-5 0.64 AML other m 2021-10-28T02:31:09.63
TDMT - Time Domain Moment Tensor
Fault Plane solutions in the area
Type Description Link
QuakeML - small Event, Origin, FocalMechanism Download
QuakeML - full Event, Origin, FocalMechanism, Amplitude, Arrival, Pick, Station Magnitude Download