Seismic hazard model MPS04-S1

DPC-INGV 2004-2006 Agreement

Project S1

Continuation of assistance to DPC for improving and using the seismic hazard map compiled according to the Prime Minister Ordinance 3274 of 2003 and planning future initiatives

Interactive Seismic Hazard Maps 2004-2006
(version 2.0 - 1 January 2019)

On line help

Introduction

This website disseminates seismic hazard model's data of Italy, released by INGv between 2004 and 2006. The new version implements only the interface for querying and showing data. Data have not been changed.

Every piece of information about the procedure adopted to estimate the seismic hazard values, their meaning or any further detailed study, refer to the home page of the S1 project: esse1.mi.ingv.it (available only in Italian)

The system allows to visualize and query probabilistic seismic hazard model of the Italian territory, represented by several shaking parameters on a regular grid spaced by 0.05°.

The maps display two shaking parameters, PGA (horizontal peak ground acceleration) and Sa (spectral acceleration); the unit of measure is g, i.e. the gravity acceleration, corresponding to 9.8m/sec^2. The disaggregation analysis is available for PGA values only.

Maps in PGA were evaluated for different probabilities of exceedance in 50 years (9 probabilities, from 2% to 81%). The distribution of the 50th percentile (median map, which is the reference map for every probability of exceedance) and of the 16th and 84th percentiles (which express the variability of each estimate) are available for each evaluation. The details about the computation of these hazard estimates are available on the page describing deliverable D2 of this project (http://esse1.mi.ingv.it/d2.html)

Maps in Sa were calculated for the same probabilities of exceedance in 50 years (9 probabilities, from 2% to 81%) and for different periods (10 periods, from 0.1 to 2 seconds) as well. Again, the distribution of the 50th percentile (median map, which is the reference map for every probability of exceedance) and of the 16th and 84th percentiles (which express the variability of each estimate) are available for each evaluation. The details about the computation of these hazard estimates are available on the page describing deliverable D3 of this project (http://esse1.mi.ingv.it/d3.html)

Users can select the parameters of the required map in the area Map Selection. Then, pressing the Redraw map button, they will get the required map.

The interface allows the user to obtain details of the selected shaking parameter in graphical format, together with the tabular data, through the instrument Chart, for every single node of the reference grid. From the PGA map the user will get the corresponding hazard curve (the PGA Vs different annual probabilities of exceedance); from the Sa map the user will get the UHS (Uniform Hazard Spectra) for different probabilities of exceedance in 50 years.

In addition, it is possible to obtain details of the disaggregation analysis of the associated PGA value in graphical and tabular format, using the button Disaggregation, for every single node of the reference grid. The mean values of M, D, and ε (the mean magnitude, distance, epsilon values that mostly contribute to the hazard) will be also returned. The details about these analyses are available on the page describing deliverable D14 of this project (http://esse1.mi.ingv.it/d14.html).

Frequently Asked Question

 

Q. How to use the buttons above the the map?
The buttons above the map are grouped according to the offered fuynctionalities:

On left there are the following navigation buttons always enabled:

At centre the following informative buttons:

On right the following buttons are always available:

Q. What are the provided hazard values?
The site provides:

Q. Why values and graphs are not always available for Sardinia and other islands?
For some areas (specifically islands areas) the methodology used at national scale did not provide reliable results. Therefore, for these areas specific analyses were performed, whose results are described in deliverable D1 of this project (http://esse1.mi.ingv.it/d1.html). Commonly for these areas only one hazard value was provided: PGA with probability of exceedance 10% in 50 years. Therefore the associated hazard curves (and related graphs) are not available. For the elastic design spectra graph, it was used that defined by Eurocode 8 for the same probability of exceedance (see the deliverable D3 of this project: http://esse1.mi.ingv.it/d3.html).
Also the disaggregation analyses are not available for these areas.

Q. How to ask for the visualization of the map for a specific parameter value?

To ask for the visualization of a specific value the user has to set the parameters to define it (in the section Map Selection on the left of the map).
Where PGA values are required the user must select the values of Probability in 50 years and Percentile.
Where Sa values are required the user must also select the value of Spectral Period, whose selector will become active in this case only.
Maps can be visualized using two different chromatic scales, one defined for MPS04 (selected by default), one defined for MPS19.
The option is available at the bottom in the section Map Selection.

Finally the user must click on the button Refresh the map to get the required map.

Q. How to get the detailed information for a specific node?
TTo get details for a single node, the corresponding shaking map must be visualized.
It is possible to get three different charts for each node of the grid:

  • Seismic hazard curves: chart of the shaking parametre PGA against annual frequency of exceedence;
  • Unifor hazard spectra: chart of the shaking parametre SA against the spectral period. One curve for each probability of exceedance in 50 years;
  • Disaggregation of the PGA parametre.

To get the first two charts (PGA and UHS) it is required to click the button Chart (in the tool bar above the map) while the map shows the required parametre. The button will turn to active:


Then click on the grid node of interest.

To get the disaggregation chart it is required to click the button Disaggregation (in the tool bar above the map) while the map shows the PGA parametre, and then click on the grid node of interest.

Charts and table data in all cases refer to the selected values shown on the map:

  • in case of PGA, the graph and table present all the available values of PGA (the annual probabilities of exceedance and the three percentiles) for the required point;
  • in case of Sa, the graph and table present the values of Sa for the selected percentile only, and for all the probabilities of exceedance in 50 years;
  • in case of disaggregation values of PGA, the graph and table present the percentage contribution to the seismic hazard of each couple of magnitude-distance values. The mean values of magnitude, distance and epsilon (ε) are also provided.

If the button Export to Pdf is selected, the user get a document in Pdf format containing the main information on the node by selecting the grid node of interest. Specifically:

  • a map at small scale of the area centred on the selected point, with the PGA values with probability of exceedence of 10% in 50 years on flat, rigid ground;
  • the hazard curves and associated table data;
  • the uniform hazard spectra (50° percentile only);
  • the disaggregation chart of PGA value for a probability of exceedance of 10% in 50 years.

Q. What is the meaning of the disaggregation graph?
For a given grid point, the disaggregation analysis of PGA values shows the evaluation of the percentage contribution to the seismic hazard estimate provided by each couple of magnitude-distance values. This information is represented in graphical and tabular format. For the point of interest are also presented, below the table, the mean values of M-D-ε.
This kind of analysis is useful to identify, in probabilistic terms, the seismogenic source, which most likely will generate the estimated shaking, which is in turn useful for the microzonation analysis. All the details on this type of analysis are inside the deliverable D14 of this project (http://esse1.mi.ingv.it/d14.html).
The disaggregation is not available for islands mentioned above.

Q. How to read the values on the map?

Referring to the selected parameter, the unit of measure of the hazard values is g (acceleration of gravity); the values corresponding to the colors showed on the map are presented in the legend on the right of the map:

Q. How to visualize the points for which it is possible to check detailed results?
The points where it is possible to get detailed data are those shown in the map when the required hazard value is visualized.
Such points are easier to identify in the lower scales.

Q. How is it possible to move on a specific point on the map?

  • To change the center point of the map, select (in the tool bar above the map) the button Centre and then click with the mouse on the point which should be the new centre.
  • To enlarge or shrink the map (within the range of the allwed scale: 50.000-5.000.000), centring on a specific point, select (in the tool bar above the map) the button Zoom+
  • or Zoom-.
  • It is possible to move the view of the map in a direction (right, left, up, down) by clicking on the corresponding edge of the map.
  • It is possible to zoom on a quadrilateral area: select (in the tool bar above the map) the button Manual Zoom, activating the functionality.
  • Move the cursor to the upper-left corner of the area to zoom; keep the mouse left button pressed and drag the cursor to the bottom-right corner to zoom. While dragging, the cursor must remain within the map, otherwise the selection is lost.
An alternative option is to provide the coordinates of the desired point in the section "Surfing" on the left of the map, in the box Coordinates of the center of the map and to provide the zoom scale required in the box Scale.
The provided coordinates become the new map center.
The main map is enclosed within four bar, one per side, which allow to move the view in the corresponding direction:
A single municipality center can be searched for through the tool Municipality Search. A minimum of three consecutive letters in the name of the municipality it is required. Then click on the button Search.
A list of Results of the Municipality Search is visulized.
In This way, after selecting the municipality from the proposed list, the municipality center becomes the new map center.
To remove the highlight of the municipality, click on the button Hide.

Q. Why borders of municipalities, provinces and regions are not always visualized?

The visibility of the administrative borders (municipalities, provinces and regions) and the associated chieftowns depends on the scale of the visualized map.
The lines of the three types of administrative borders are different, as shown in the following figure:

Q. How to know which part of Italy is actually represented on the main map?

Near the map, on the top right, a little map of Italy where is pointed out the visualized area is always present.