Tsunami risk. Activities
Over the centuries, Mediterranean coasts have been affected by numerous tsunami events arising from earthquakes. In view of the exposure to this risk of the Italian coasts, on February 17, 2017, the directive of the President of the Council of Ministers establishing the National Alerting System (SiAM) for tsunamis generated by earthquakes in the Mediterranean Seas was signed, under the coordination of the Civil Protection Department.
Within this system, the INGV - National Institute of Geophysics and Volcanology - operating through the Cat (Tsunami Alert Center) - has the task of assessing, in its area of competence, the possibility that an earthquake of magnitude equal to or greater than 5.5, with epicenter at sea or near the coast, may generate a tsunami and estimate the time of arrival of the wave along the different stretches of coast. The tideographic data provided by Ispra - Superior Institute for the protection and the environmental research allow to confirm or not the possibility that a tsunami will occur. On the basis of Cat evaluations, the Department of Civil Protection - through the Situation Room Italy - has the task of spreading the warning messages to activate, in the shortest possible time, the National Service of Civil Protection.
In implementation of the provisions of the Directive establishing the SiAM, on November 15, 2018, the Decree of the Head of Department containing the guidelines for updating the civil protection plans for the tsunami risk was published in the Official Gazette. The main purpose of the measure is to provide the various components and operational structures of the National Service with elements related to this specific risk and useful for civil protection planning, for the protection of the population along the coasts.
With regard to the SiAM, it is important to underline that, although scientifically accurate and rapid forecasting of tsunamis has accomplished significat progress in recent years, it is not always possible to issue a timely alert. Also, the assessment carried out by the Ingv Cat does not ensure the certainty that after the issuance of the alert, a tsunami will occur, and does not even ensure that the impact of a tsunami on the coast will be always preceded by the issuance of the alert message. Moreover, in the case of tsunamigenic earthquakes close to the Italian coast, the arrival of SiAM warning messages could take place in areas close to the earthquake point of origin, in insufficient time to activate preventive measures to protect the population. Therefore, it is fundamental that the citizen knows how to recognize the precursors of a tsunami event and knows the rules of self-protection. For this reason, it is important to start prevention activities, aimed at reducing the risk and disseminating knowledge of civil protection.
With regard to SiAM, two alert levels are adopted. They are based on the estimated severity of the tsunami on the Italian coasts. These levels, as well as the estimated arrival time of the first tsunami wave on the coast are estimated at forecast points corresponding to specific geographical coordinates (located along the coast). In analogy to the alert levels adopted throughout the Mediterranean, the alert levels are:
- Orange (Advisory): indicates that the Italian coasts could be affected by a tsunami wave with a height of less than 0.5 meters and/or with a run up of less than 1 meter;
- Red (Watch): indicates that the Italian coasts could be affected by a tsunami wave with a height of more than 0.5 meters and/or with a run up of more than 1 meter.
"run up" means the maximum topographic altitude reached by the tsunami wave during its flooding with respect to the average sea level.
The coastal areas to evacuate in case of Orange or Red alert are specified in the flood maps issued by Ispra. Here, the Orange alert level is associated with the "alert zone 1" while the Red alert level is associated with the "alert zone 2". According to the broadness of the alert zones, their vulnerability, and the characteristics of the clearance routes and the operational capabilities of the territorial system, municipalities may consider whether to maintain two separate alert zones, or alternatively, to merge them into a single zone ("single zone - red/orange alert"). These maps can be consulted at the link http://sgi2.isprambiente.it/tsunamimap/ where, currently, only those relating to the alert zones for the Regions of Calabria and Sicily are available.
Maps elaborated by Ispra, even preliminary, have been realized according to a methodology used and acknowledged at the international level. They are based on a recent model of hazard probability for tsunamis generated by earthquakes (S-PTHA, Seismic - PTHA), produced within the project TSUMAPS-NEAM, co-financed by DGECHO and coordinated by INGV. Further details are available in Allegato 1 alle Indicazioni operative(2191 Kb). At the moment, they represent the most accurate available information on the basis of the data accessible at national level. As such, they can be further refined according to the data quality and resolution of the cartographic charts and the evolution of the processing methodologies..
The SiAM tsunami warning messages are issued when the INGV Cat records a seismic event, which can have significant impact on the italian coasts. The alert message may be associated with two alert levels: red or orange.
Alert messages can be followed by messages of:
- update, when, on the basis of new data acquisitions or re-elaborations of an event, some changes occur in the estimation of seismic parameters that can determine an increase in the alert level with respect to those already issued;
- revocation, when the recorded seismic event does not give rise to the tsunami event or causes a very low magnitude tsunami. This message invalidates the previous alert message;
- confirmation, when the analysis of sea level data records the instrumental confirmation of tsunami waves. This message is issued following an alert or alert update;
- end of an event, is issued at the conclusion of the tsunami, when the changes in sea level observed on the marigraph are comparable with the levels recorded before the tsunami. This message concludes all early warning messages issued in relation to the same event.
Within SiAM, it is also issued a message of:
- information, which is not an alert but indicates that it is unlikely that the tsunami wave would have significant impact on the Italian coasts, nevertheless, within 100 km from the earthquake's epicentre, variations in currents and anomalous wave movements can be generated.
Alerts distribution, must necessarily take place in a short time, thus the Civil Protection Department - which operates within the SiAM - cannot rely on the procedure normally used for other civil protection risks, in which alerts are spread through the Regions and/or Prefectures.
In this context, the Department has developed the SiAM Technology Platform, capable of simultaneously dispatching alert messages to a different group of parties - including Components, Operating Structures and Service Providers - identified in Annex 2 of the SiAM Directive and subsequently integrated into Annex 2 of Operating indications (154 Kb). It should be noted that the Platform does not directly reach the population, which should be alerted through the procedures defined in the municipal civil protection plan together with the plans of the other territorial levels.
The Platform has been developed to automatically receive the warning messages from the INGV CAT, which contain the indication of potentially tsunamigenic seismic events. Once verified the formal validity of the messages, the Platform will start the transmission to all the addresses in its registry, following a dual distribution channel that provides for the sending of SMS and email. Moreover, the use of IVR - Interactive Voice Response - is under development.
The general strategy adopted in the Operational guidelines for the protection of the population in the event of a tsunami is the preventive evacuation of the population in risk coastal areas. It can be done either vertically, when the highest floors of the buildings or higher topographical heights of the coast are reached ( see Annex 3 to operative indication - 53 Kb) or horizontally, when people move away from the coast at risk towards the hinterland. The strategy translates into activities and safeguard measures, which are further explained in the Operating Instructions.
Particularly:
In the case of a red or orange warning message, the only operational phase that can be activated is the Alarm phase, since the tsunami originates from an unpredictable event and its ignition takes place in a limited span of time that precludes the activation of previous operational phases. During the Alert operational phase, operators will intervene to facilitate the evacuation of the population and the securing of the infrastructures on the territory. Thus, during this stage, the coastal municipalities must implement their emergency plans and activate the procedures to alert the population; regions have to implement the procedures for managing the flow of information with the coastal municipalities involved in the alert; the operational structures, regions, provinces and prefectures-UTG must implement the necessary actions to support municipalities, as far as they can, activating - if required - their sector plans. In this phase, the Department of Civil Protection evaluates the possible convocation of the Operational Committee and with INGV and ISPRA, follows the evolution of the alert providing updates. The Department is also responsible for providing information to the press.
Updating and Confirmation messages, containing information on alert levels, are also associated with the Operational Alarm Phase.
When an information message is issued, the main measures involve the territorial level - such as municipal administrations and operational structures - and consist in information activities addressed to the population, aimed at providing information about the ongoing event and monitoring the effective use of resources available. At national level, SiAM activities consist in monitoring the evolution of the event; particularly, the Department maintains a close link with operational structures and coastal regions to monitor any critical local situations and also provides information to the press.
In the event that a tsunami occurs, affecting partially or totally the coastline alerted, even before receiving End of Event message, the operational actions related to the emergency management provided in the territorial plans must be implemented. The operational response should be based on the consequences occurred on the territory, ranging from the municipal level activation, up to the activation, if necessary, of the entire National Service of Civil Protection. In relation to the current situation and on the basis of operational needs, it may be necessary to convey the Operational Committee by the Civil Protection Department - unless already activated during the Alarm phase - or the establishment of a Di.Coma.C., to ensure the coordination of on-site emergency management.
Finally, in the case of a Revocation message, which is always preceded by an Alarm message, even though a tsunami did not occurred, it may be necessary to manage the activities to return to normal situation. Furthermore, information regarding the message issued and information regarding the modalities for returning to the conditions in place before the alert should be sent to the population.
In implementation of the Directive establishing the SiAM, the Department's operational guidelines are intended to provide the territorial levels (Regions, Provinces, Municipalities), operational structures and managers of essential services and mobility useful elements for the elaboration or updating of their civil protection plans.
The indications provide that the territorial level plans must be articulated according to the different SiAM messages. Also, the various levels should decline the information received from the national level in specific procedures able to respond to the specific needs of the territory. With regard to the action plans for managing the emergency, these should match those for seismic risk, but tailored to a different type of risk. Particularly for tsunami risk, it is necessary to verify that the headquarters of the coordination centres and the emergency areas are not located in areas within warning zones 1 or 2.
Regional and provincial plans must guarantee the necessary support to the activities of coastal municipalities in the phases of planning, population alerting and emergency management, and provide for specific activities in accordance with their institutional roles. Regions, for instance, should promote exercises, studies and insights (in terms of danger, vulnerability of the building and removal routes, evacuation methods, etc..) taking into account both the exposure to risk and the available resources. The Prefectures have to define the modalities of public order management in order to facilitate the "supervised" evacuation.
The most significant part of the operational guidelines on civil protection planning is addressed to municipalities. Particularly, the document envisages the organization of the municipal plans in four main sections, containing indications on the dangerousness of the coasts and alert zones, the procedures to alert the population; the model of intervention and the main activities and information and communication activities. Moreover, in the description of the intervention model, it is recommended to municipalities to identify in their Civil Protection Plan the methods for keeping the population away from the coast at risk to guarantee an effective distancing of the population. It is also suggested to evaluate the possibility of preparing an emergency signal, for which a model is provided in Annex 4 to the Operational Indications (2578 Kb).
On the basis of the general strategy outlined in the Operational Guidelines, the operational components and structures receiving the alert messages must prepare the plans to integrate their intervention in the field of civil protection, activating national and territorial levels in compliance with the internal organization and their command and control network. These domestic plans should be organized so as to provide safeguard of instrumental and human resources in risk areas. The Maritime Authority and the Prefectures - UTG together with the State Forces present on the territory should elaborate a specific sector planning.