Aon Benfield says central and southern Italy should take steps to reinforce poorly constructed buildings
Following the first anniversary of the L’Aquila earthquake, a new research report from the Aon Benfield’s Hazard Research Centre shows how central and southern Italy should prepare for the possibility of larger earthquakes and take steps to reinforce poorly constructed buildings.
The L’Aquila event resulted in the highest earthquake death toll in the EU since the 1980 Irpinia earthquake in Italy and the highest economic loss due to seismic activity since the 1999 Athens earthquake.
Research undertaken by Dr. Ioannis Papanikolaou, author of the report and academic at the Aon Benfield UCL Hazard Research Centre, identified the following key findings to assist seismic hazard assessment, planning and recovery:
• The L’Aquila earthquake was not a surprise – it occurred in an area characterized as having high seismic hazard based on traditional maps and historical record
• The event ruptured a small segment of the fault system and not one of the major postglacial fault scarps in the area. This explains the minor primary surface ruptures which did not exceed 4km in length or 10cm in displacement. Other surrounding faults, however, can produce much stronger earthquakes that can generate primary surface ruptures of 15-20km long and maximum displacements exceeding 1m
• Satellite imagery showed that the earthquake resulted in a maximum subsidence of 25cm and uplift of 10cm
• Bedrock geology and basin effects played a decisive role in the damage pattern even at short distances. For example, communities that were only 1.5km apart recorded differences in shaking intensity of up to 3.5 degrees (ranging from no damage to poor quality buildings in one community to severe damages to specially designed structures in the neighbouring community)
• The majority of damage in the villages occurred due to poorly constructed and old masonry buildings, while collapses in reinforced concrete buildings were relatively few in number. However, despite the fact that their reinforced concrete frames remained intact they experienced crumbling masonry and collapsed fill walls. This suggests that the nature of the infill walls and their attachment to the frame of the buildings should be re-examined.
Papanikolaou commented: “The L’Aquila earthquake is an important case study for two key reasons. Firstly, moderate magnitude earthquakes occur more often than strong events in extensional settings where the earth’s crust is being stretched. For example, Italy experiences a couple of moderate damaging events every decade compared to one or two stronger earthquakes every century. Secondly, the frequency of these types of moderate earthquakes is combined with their proximity to population centres which presents a high risk. Given the moderate size of the earthquake, the high level of structural damage and the sizeable casualty figures, emphasis must be placed on ensuring that the historical centers are better prepared next time as larger earthquakes are a possibility.”
Maurice Cox, General Manager, Italy for Aon Benfield, said: “A low take up of earthquake insurance in Italy meant that L’Aquila was not a large loss for insurers. However, the benefits of earthquake insurance are becoming apparent following the devastation, and we’re beginning to see insurers considering stepping in to provide catastrophe cover for residential and commercial property – particularly in the absence of a government scheme. To achieve this, insurers will need to improve monitoring of exposures and access to construction data, while taking greater control over their risk accumulation to both support the region and create a profitable line of business.”
Paul Miller, head of international catastrophe management at Aon Benfield, added: “Events such as L’Aquila provide us the opportunity to further test and improve the vulnerability functions within catastrophe models using actual loss data. Any resulting enhancements to the catastrophe models can help to reduce uncertainty around the risk and will allow insurers to make more informed decisions about offering earthquake cover in the region.”
