CLASS 1.0 Quality selected locations, shallow (top) and deep (bottom)

Catalogo delle Localizzazioni ASSolute (CLASS)

Landing page of the Catalog of Absolute (non linear) 3D earthquakes Locations of the Italian region from 1981 to 2018.

Downloads: to download the phases (text) files please use the drop-down menu "CSI 2.0 (Phases 1981-2008)" in the top-bar of this website. Phases from 2009 to 2018 in QML format are available at INGV Terremoti web portal.
To download the whole catalogs in "zipped csv" or "zipped kml", or the single year text files, or to select through the webservice, please use the drop-down menu "Download Locations" in the top-bar of this website.

Citation: to cite this dataset please reference both the following DOIs:

[Paper]: Latorre D., Di Stefano R., Castello B., Michele M., Chiaraluce L. (2023)
"An updated view of the Italian seismicity from probabilistic location in 3D velocity models: The 1981–2018 Italian catalog of absolute earthquake locations (CLASS)".
 https://doi.org/10.1016/j.tecto.2022.229664.

[Data set]: Latorre D., Di Stefano R., Castello B., Michele M., Chiaraluce L. (2022)
"Catalogo delle Localizzazioni ASSolute (CLASS): locations (Version 1). Istituto Nazionale di Geofisica e Vulcanologia (INGV)."
https://doi.org/10.13127/class.1.0

Creative Commons Attribution 4.0 (CC BY 4.0)

Introduction


The catalog named CLASS (acronym for “Catalogo delle Localizzazioni ASSolute”), is a catalog of earthquake locations computed in a 3D velocity model of the Italian region with a probabilistic approach and a non-linear inversion method.

CLASS is currently the most complete and homogeneous hypocenter location catalog of earthquakes recorded in Italy from 1981 to 2018: it includes more than 420,000 events relocated by inverting ~5.0 million P and ~3.5 million S wave first arrival times resulting from a collection of instrumental seismicity data recorded in Italy, in the wake of the CSI catalog by Chiarabba et al. (2005) and Castello et al. (2006), and enriched with new integrated seismic wave arrival times from both the INGV and other Italian permanent networks datasets.

Input Data

P- and S-readings: CSI 2.0 phase integrated dataset for the period 1981-2008 and, from 2009 to 2018, the sole Italian Seismic Bulletin (INGV);
Magnitudes: a compilation of several several sources for magnitude essentially based on CSI1.1 and INGV.

Location and Quality

Probabilistic locations with NLL code by A. Lomax, in a tomographic 3D velocity model, with stations corrections; validity of the hypocenter locations assessed “a posteriori” by analyzing the inversion solutions attributing a quality class (A-->D and a numerical range).

Product

CLASS catalog, including 3d proabilistic hypocenters, Probability Density Function, formal errors, catalog-consistent quality classification, preferred CLASS magnitude and INGV magnitudes.

Mobirise Website Builder

Input Data: P and S-wave arrivals and magnitudes

The dataset of P and S wave arrival times combines the CSI 2.0 phase integrated dataset for the period 1981-2008 with the Italian Seismic Bulletin phase dataset of the INGV for the period 2009-2018.
Magnitudes in CLASS are not recomputed but obtained from previous available catalogs when this information is present. Magnitudes are generally local magnitudes (ML) whenever it is possible and within the range of the ML reliability. This is for the sake of homogeneity and completeness in a variety of studies.

For events of the period 1981-2002 the CLASS magnitudes are inherited from the CSI catalog (Castello et al., 2007). For events without magnitude estimation in CSI, this information is extracted from the ISIDe database (ISIDe Working Group, 2007), giving priority to the Md (duration) INGV reference magnitude at that time. For events of the period 2003-2018, the CLASS magnitudes are extracted from the ISIDe database, which also includes all the solutions from the BSI bulletin, giving priority to the ML and within the range of the ML reliability.

Mobirise Website Builder

Earthquake Hypocenter Locations and Quality Assessment

The Italian seismicity is relocated in the 3D Italian tomographic model of Di Stefano and Ciaccio (2014) using the probabilistic, nonlinear earthquake location software package NonLinLoc (Lomax et al., 2000; Lomax et al., 2014; Anthony Lomax web page).

The validity of the hypocenter locations then is assessed “a posteriori” by analyzing the inversion solutions. NonLinLoc provides a complete description of the hypocenter location uncertainties, whose main estimators described in Table 1 are included in the quality analysis proposed by Michele et al. (2019). For each earthquake we compute a quality factor Qf by applying the empirical formula, in which the subscript n means “normalized”, wj are the weights and Nest the number of estimators.
The Quality factor Qf is a normalized value from 0 to 1. In order to set up a simple way for selecting events in our catalog, we associated each location quality factor to a Quality Class having code from A (best location with quality factor from 0 to 0.25) to D (worst location with quality factor from 0.75 to 1). Map views show the distribution of the earthquakes selected by Quality Class (A-class, B-class, C-class, and D-class).


Product

The probabilistic hypocenter location of ~400,000 earthquakes 1981-2018 is here released, with location quality parameters, a quality class attributed (A-->E), a set of available magnitudes, and (when possible) the ID of the INGV monitoring system to retrieve additional information as for example resentment, focal mechanism/TDMT, shakemaps.
Please refer to the Menù at the top of this site to download the .csv.gzip or the .kml.gzip or to use the dedicated webservice to download the product.
Here below the CSV file and webservice output format are detailed.

1

Unique identification numbers

id_class is unique number of class_events; from 1981 to 2008 it corresponds to the CSI 2.0 id while from 2009 to 2018 it is identical to id_ingv
id_ingv is the unique number of seismic events given by the INGV monitoring system
id: in the last column an internal database number is reported 
2

CLASS Hypocenters fields

origintime (of the earthquakes), probabilistic latitude, longitude, depth (positive downward)
3

Magnitudes

magnitude_class is the preferred among the available ones (possibly an ML)
magnitude_class_type is the source/type of the selected value
magnitude_ingv_loc is the estimate that INGV attributed to its own location (1981-2004 tipically Md and a few ML, 2005 on tipically to "almost only" ML)
magnitude_ingv_loc_type is the source/type of the selected value
magnitude_ingv_pref is the best available estimation that INGV attributed to the earthquake up to the last check (it can be the magnitude_ingv_loc itself or the Mw)
magnitude_ingv_pref_type is the source/type of the selected value
4

Quality parameters

rms: root mean square error from P and S arrival time residuals (s)
errh: hypocentral error on horizontal coordinates computed from the 68% ellipsoid error (km)
errv (errz): hypocentral error on vertical coordinates computed from the 68% ellipsoid error (km)
nphs: number of arrival time picks used in the hypocenter location inversion
gap: maximum azimuthal angle between two successive stations around the source epicenter (degrees)
mindist (sdist): minimum station epicentral distance (km)
pdfray (Rpdf): radius of a sphere having volume equivalent to the PDF volume (km)
locd: distance between the probabilistic hypocenter and the expected linear location hypocenter (km)
qmd_cha: quality class expressed as text A (top) to D (worst) and E (depth not for any use)
qmd_num: quality class expressed as continuous floating numbers from 1 (top) to 0 worst (excluding E which is out of the range)

Web page concept, contents, realization, maintenance by:
R. Di Stefano
D. Latorre
B. Castello
M. Michele
L. Chiaraluce

Made with ‌

Easiest Website Builder