CFTIlandslides, an Italian database of landslides caused by historical earthquakes

The information in the CFTIlandslides10 dataset is based on a review of the impacts of earthquakes on the environment originally provided by the CFTI5Med earthquake catalogue (https://storing.ingv.it/cfti/cfti5/)6,8, which has been improved and expanded using different sources of information (Figure 3).

Fig. 3

Our assembly, installation, and analysis workflow (see Figure 2).

Since CFTIlandslides10 is designed as a continuously updated repository, the earthquake sequences associated with HEILs have been classified, based on the level of current knowledge and depth of analysis (Table 1). However, the version described here is the first version published and registered in the INGV data registry. Future versions will have a different DOI.

Data collection and synthesis

The historical information available on earthquake-induced landslides is vast and documented in various paper and digital files. Some of it consists of text and icons; in some cases, natural scientists and geologists have described the effects, and in other cases it appears in news stories told by ordinary witnesses or newspapers. Given the diverse and complex nature of the primary information body, interpreting the various data and summarizing it in an organized table was a crucial part of the work.

To achieve this goal, the review process went through three successive steps:

1)

Review historical sources, newly found or already archived in the CFTI6 database.

We analyzed different types of documents, including texts, letters, reports, newspapers, photographs, and maps (Figure 4). We reviewed more than 800 documents obtained from public and private libraries and archives and the Internet. Of these documents, more than half contained useful information. The careful analysis of the sources allowed us to collect new evidence on landslides and more detailed descriptions of landslide impacts already included in the CFTI6 database.

Figure 4

Examples of historical sources. (a) Original historical report of the 1783 Calabrian earthquakes16; (b) Photograph of the Monte Epomeo landslide following the 1883 Ischia earthquake (Johnston Lavis Collection of Geology, University College London)17; (c) Map of the landslides that occurred between Favazzina and Bagnara following the 1908 Messina Strait earthquake18.

2)

Analysis of recent scientific articles and technical reports.

We have collected and examined the latest scientific literature describing the effects of earthquakes in the Italian territory, searching for new evidence emerging from historical sources unknown to the CFTI6 database. We have collected 569 bibliographic references, including historical sources, scientific articles and technical reports, all of which contain information on landslides caused by earthquakes; they are listed in the CFTIlandslides10 bibliography. All these references are stored in the CFTI6 database with a unique identification code; 436 of them are publicly available in PDF format and can be downloaded from the CFTIlandslides10 website.

3)

Compared to other digital archives.

We searched the CEDIT11 (https://doi.org/10.4408/IJEGE.2012-02.O-05) and EEE12 (http://eeecatalogue.isprambiente.it/) catalogues for any description of HEILs effects not already included in our dataset. For each retrieved effect, we checked the original reference, available information, and description.

After completing these three steps, we combined and summarized the data collected from different sources into a single text file. The information was archived based on the name of the landslide site. Under each site, we reported the identification code for each historical source and the original descriptive text associated with the hill. This step allowed us to represent the entire data set in a tabular form, containing all relevant information and the initial geographic location of each hill (see the Data History section).

data analysis

The geographic information provided by historical sources allowed us to identify, at least initially, the effects of each individual landslide, and to display them in a GIS environment; especially the detailed and comprehensive description that often allowed us to improve this site significantly. The best possible location for each landslide was determined using satellite imagery, historical and topographic maps, and toponymic maps.

When the texts of historical sources allowed us to identify the type of landslide movement, we followed the classification adopted in the IFFI database (Figure 5).

Figure 5

Distribution of landslides caused by earthquakes by type of movement.

After site analysis, landslide impacts were divided into three categories according to site accuracy (Figure 6):

Category A: The property is well located geographically by a clear site name, detailed indication or name. Examples of descriptions are “… on the left corner of Casa Baroncioni…” or “… at kilometer 56 of the regional road…”;

Category B: The impact is over a large, defined area, but no further description is available. Examples of such descriptions include “… on land near the north-western part of the village…” or “… along the railway line between Scilla and Vavazzina…”;

Category C: Impact is linked to the CFTI6 database location, but there is no specific geographical indication.

Figure 6

Distribution of landslides caused by earthquakes by location accuracy (see text for definition of each accuracy category).

Assignment to one of the three categories depends on the quality of historical information and the ability to locate the impact on modern maps; it is not a metric value.

Furthermore, the location of each landslide impact of categories A and B was compared with the location of all individual landslides listed in the Italian Landslide Inventory (IFFI database)14: when a satisfactory geographical match with a landslide in the IFFI Landslide Inventory was found, the two items were paired.

For this specific case we created two additional classes:

The type of landslide movement described in historical sources almost always corresponds to the landslide characteristics provided by the IFFI, with two recurring exceptions:

a)

Lack of information from historical sources: In this case, we adopted the landslide classification of the associated IFFI record;

B)

Based on the corresponding IFFI record, we reported some complex landslides that were described by historical sources as rockfalls.

The dataset in tabular format and GIS project format are designed to collect information and consult HEILs individually and on the map. These two products are interlinked to improve data quality. When a landslide site name mentioned in historical sources is found on a GIS project map, the associated coordinates are reported in the dataset in tabular format. Otherwise, if the name of a historical landslide site changes and contemporary maps report a new place name, the dataset in tabular format is updated accordingly.

CFTI Landslide Dataset

The CFTIlandslides10 dataset is published under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. It currently includes 1058 landslides that can be viewed and downloaded from the dedicated INGV website (https://doi.org/10.13127/cfti/landslides), which can also be accessed from the recently renovated CFTI portal of the Istituto Nazionale di Geofisica e Vulcanologia (https://cfti.ingv.it)15. The metadata is also archived in the INGV data registry, which is publicly accessible through the Istituto Nazionale di Geofisica e Vulcanologia Open Data Portal (https://data.ingv.it/dataset/964).

To make CFTIlandslides10 data publicly available through the website we have developed:

a)

Custom WebGIS application (Figure 1, 7);

Figure 7

The CFTIlandslide WebGIS application also allows the data to be viewed on a 3D terrain map. Here, the impacts of earthquake-induced landslides are shown on an aerial photo map together with the topography of the digital terrain model and compared with IFFI landslide data (via the ISPRA WMS service). An example of the full data sheet available for each landslide impact is shown in the upper left.

B)

Open Geospatial Consortium web services (https://www.ogc.org/) (Table 2).

Table 2 OGC web services available for the CFTIlandslides dataset.

Through OGC Web Services, data can also be downloaded in CSV (Comma Separated Values), SHP (Esri Shapefile), KML (Keyhole Markup Language), or GeoJson files.

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