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Reconnaissance work is built into the earthquake modeler’s job description – the backpack is always packed and ready. Large earthquakes are thankfully infrequent, but when they do occur, there is much to be learned from studying their impact, and this knowledge helps to improve risk models.

An RMS reconnaissance team recently visited Ecuador. Close to 7pm local time, on April 16, 2016, an Mw7.8 earthquake struck between the small towns of Muisne and Pedernales on the northwestern coast of Ecuador. Two smaller, more recent earthquakes have also impacted the area, on July 11, 2016 an Mw5.8 and Mw6.2, fortunately with no significant damage.

April’s earthquake was the strongest recorded in the country since 1979 and, at the time of writing, the strongest earthquake experienced globally so far in 2016. The earthquake caused more than 650 fatalities, more than 17,600 injuries, and damage to more than 10,000 buildings.

Two weeks after the earthquake, an RMS reconnaissance team of engineers started their work, visiting five cities across the affected region, including Guayaquil, Manta, Bahía de Caráquez, Pedernales, and Portoviejo. Pedernales was the most affected, experiencing the highest damage levels due to its proximity to the epicenter, approximately 40km to the north of the city.

Sharing the Same Common Vulnerability

The majority of buildings in the affected region were constructed using the same structural system: reinforced concrete (RC) frames with unreinforced concrete masonry (URM) infill. This type of structural system relies on RC beams and columns to resist earthquake shaking, with the walls filled in with unreinforced masonry blocks. This system was common across residential, industrial, and commercial properties and across occupancies, from hospitals and office buildings to government buildings and high-rise condominiums.

URM infill is particularly susceptible to damage during earthquakes, and for this reason it is prohibited by many countries with high seismic hazard. But even though Ecuador’s building code was updated in 2015, URM infill walls are still permitted in construction, and are even used in high-end residential and commercial properties.

Without reinforcing steel or adequate connection to the surrounding frame, the URM often cracks and crumbles during strong earthquake shaking. In some cases, damaged URM on the exterior of buildings falls outward, posing safety risks to people below. And for URM that falls inward, besides posing a safety risk, it often causes damage to interior finishes, mechanical equipment, and contents.

Across the five cities, the observed damage ranged from Modified Mercalli Intensity (MMI) 7.0-9.0. For an MMI of 7.0, the damage equated to light to moderate damage of URM infill walls, and mostly minimal damage to RC frames with isolated instances of moderate-to-heavy damage or collapse. An MMI of 9.0, which based on RMS observations, occurred in limited areas, meant moderate to heavy damage of URM infill walls and slight to severe damage or collapse to RC frames.

While failure of URM infill was the most common damage pattern observed, there were instances of partial and even complete structural collapse. Collapse was often caused, at least in part by poor construction materials and building configurations, such as vertical irregularities, that concentrated damage in particular areas of buildings.

Disruption to Business and Public Services

The RMS team also examined disruption to business and public services caused by the earthquake. A school in Portoviejo will likely be out of service for more than six months, and a police station in Pedernales will likely require more than a year of repair work. The disruption observed by the RMS team was principally due to direct damage to buildings and contents. However, there was some disruption to lifeline utilities such as electricity and water in the affected region, and this undoubtedly impacted some businesses.

RMS engineers also visited four public hospitals and clinics, with damage ranging from light to complete collapse. The entire second floor of a clinic in Portoviejo collapsed. A staff doctor told RMS that the floor was empty at the time and all occupants, including patients, evacuated safely.

Tourism was disrupted, with a few hotels experiencing partial or complete collapse. In some cases, even lightly damaged and unaffected hotels were closed as they were within cordoned-off zones in Manta or Portoviejo.

Tuna is an important export product for Ecuador. Two plants visited sustained minor structural damage, with unanchored machinery requiring repositioning and recalibration. One tuna processing plant reached 100% capacity just 16 days after the earthquake. Another in Manta reached 85% capacity about 17 days after the earthquake, and full capacity was expected within one month.

The need for risk differentiation

Occupancy, construction class, year built, and other building characteristics influence the vulnerability of buildings and, consequently, the damage they sustain during earthquakes. Vulnerability is so important in calculating damage from earthquakes that RMS model developers go to great lengths to ensure that each country’s particular engineering and construction practices are accurately captured by the models. This approach enables the models to differentiate risk across thousands of different factors.

Residential insurance penetration in Ecuador is still relatively low for commercial buildings and privately owned or financed homes, but higher amongst government-backed mortgages, as these require insurance. The knowledge gained from reconnaissance work is fundamental to our understanding of earthquake risk and informs future updates to RMS models. Better models will improve the insurance industry’s understanding and management of earthquake risk as insurance penetration increases both here and around the world.

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Canada Earthquake: A Shifting Landscape

This blog is a reprint of an article published in Canadian Underwriter New insights often challenge the established view. The view of earthquakes in Canada is changing, including shifts in the seismic risk within the greater Metro Vancouver area and in the balance of seismic risk between the east and west. Starting with Metro Vancouver, insured seismic risk was previously viewed as being more heavily concentrated in the city proper, given the exposure concentration, including a prevalence of high-value buildings. But based on insights, the product of a new RMS model focused on earthquake risk in Canada, it appears insured seismic risk is driven more by exposure in the expansive region to the south of Vancouver, which straddles the main arm of the Fraser River. Why is this region in focus? It is worth examining how it was created. For thousands of years, the Fraser River carried sand, silt, and other sediments westward towards the Georgia Straight, helping to create a network of islands. Today, these islands and their surroundings are home to the fast-growing City of Richmond, the Vancouver International Airport, Deltaport container terminals and more, all of which sit on top of what geologists call a sedimentary basin. The portion of the basin to the south of Vancouver, call it the Vancouver Basin, has deposits of soft soils as deep as 300 meters. The Vancouver Basin accounts for about 10 percent of the total earthquake-exposed value within British Columbia, but contributes about 20 percent of the province’s modeled insured (or gross) average annual loss and 500-year return period loss (for this particular article, earthquake-exposed value — that is, after taking into account penetration rates, but before applying policy terms — and modeled loss considers all lines of business and coverages, although not high-value specialty occupancies, such as power plants, which were removed to generate results that reflect more typical insurance portfolios). In contrast, the City of Vancouver accounts for about 13 percent of British Columbia’s total earthquake-exposed value while contributing about 15 percent of the modeled insured average annual loss and 500-year return period loss. Key Considerations It is tempting to attribute this shift to differences in growth patterns between the City of Vancouver and the Vancouver Basin. But analysis indicates the new view of risk is driven by improvements in seismic risk modeling and not changes in insured exposure. Ground Motion Ground motion amplification that occurs during earthquakes is a key consideration. Softer site conditions, such as those made up of silts and clays, tend to amplify shaking compared with stiffer site conditions, such as those made of rock. This amplification has been observed in past earthquakes and contributed, for example, to the heavy damage in the Marina District of San Francisco, following the magnitude 6.9 Loma Prieta Earthquake in 1989. Although ground motion amplification can occur anywhere there are soil deposits, the magnitude of the amplification is even more pronounced for buildings on sedimentary basins, such as is the case in the Vancouver Basin. Figure 1: Map of Vancouver Basin. Darker colors indicate deeper deposits of soft soils.The geologic structure and deep deposits of soft soils within a basin amplify shaking several times greater than would otherwise be observed for taller buildings. For example, the sedimentary basin beneath Mexico City, coupled with inadequate design and construction standards, resulted in the collapse of more than 400 buildings following the magnitude 8.0 Michoacán Earthquake in 1985. The magnitude of ground motion amplification depends on a number of factors, including the magnitude of an earthquake, the distance between the earthquake source and the site, the depth of the basin and the characteristics of a particular building. In general, shaking can be as much as two to four times greater for taller buildings within basins compared with those located on rock. Modeling techniques that only consider the surface soil conditions generally underestimate the ground motion amplification within basins. But recent research by Sheri Molnar at the University of Victoria and scientists at Natural Resources Canada and elsewhere have provided important data to improve modeling the potential impact of amplification. Liquefaction Predicting where liquefaction will occur is another important feature of modeling to identify risk. Liquefaction — a process in which loose and saturated sandy soil transforms into a semi-liquid state during strong earthquake shaking — was a major cause of damage during the 2010-2011 Canterbury earthquake sequence in New Zealand. One of the tremors, the magnitude 6.3 Lyttelton Earthquake in 2011, led to widespread liquefaction in the City of Christchurch, especially along the Avon River, which cuts through the city. The liquefaction caused the ground to vertically settle and, especially closer to the river, move laterally, undermining building foundations. The destruction and loss of life from these earthquakes was tragic, but the events provided a huge opportunity to learn, acting as a laboratory for the earthquake engineering community. The billions of dollars in claims data, in addition to numerous studies by academics and practitioners, has resulted in a vastly improved understanding of the conditions necessary to cause liquefaction and its impact on the built environment. One observation from Christchurch is that shallow ground water acts as a sort of fuse for liquefaction, and without it, regardless of other conditions, the process will not occur. Another observation is that the severity of liquefaction varies significantly over short distances. Maps of liquefaction severity following the Lyttelton Earthquake show dramatic differences in liquefaction over areas just tens of meters apart. This is especially true close to water channels because of the prevalence of loose soil and their “open faces,” which allow the ground to displace laterally. Figure 2: Liquefaction contribution to modeled insured average annual loss in the City of Vancouver, the Vancouver Basin and surrounding area.The Fraser River Delta in British Columbia has all of these liquefaction triggers present: shallow ground water; loose, sandy soil; and a web of river channels. It also has the most important trigger of them all, nearby faults and the Cascadia Subduction Zone, with the capacity to produce large earthquakes. Lower Insured Seismic Risk Looking north of the Fraser River, towards the City of Vancouver, modeled insured seismic risk has reduced. Ironically, this is partly driven by reduced modeled ground motion amplification and liquefaction in the city, but there are other important factors at play. For example, some types of reinforced concrete buildings that are common in the city are now viewed as less vulnerable than they were previously because engineers now better understand their seismic performance. Looking towards the east, to the provinces of Ontario and Quebec, modeled insured loss (average annual loss and the 500-year return period loss) for these provinces has reduced by more than 40 percent. This change is driven primarily by an improved understanding of seismic hazard within the St. Lawrence River Valley, home to the cities of Montreal and Quebec City, among others. This leads to another important shift in Canada’s overall modeled insured seismic risk, considering a nationwide perspective. With seismic risk reducing in Ontario and Quebec while remaining relatively stable in British Columbia as a whole, seismic risk is even more heavily concentrated in the west. British Columbia now accounts for almost 65 percent of the country’s insured modeled average annual loss and about 75 percent of the 500-year return period loss. While changes in risk modeling drive this new view, it is important to acknowledge that earthquake insurance take-up is much lower in Ontario and Quebec than it is in British Columbia. Risk modeling techniques have improved in recent years, thanks to the advances in earthquake science and engineering, as well as lessons learned from past earthquakes. These advances provide insights into a changing insured seismic risk landscape across Canada. The insurance industry should be aware of these changes and strive to use these emerging insights in their business decisions.…

 Senior Product Manager, Model Product Management, RMS
Justin Moresco
Senior Product Manager, Model Product Management, RMS

Justin is a senior product manager in the Model Product Management team, focusing on RMS Latin America, Caribbean and Canada earthquake models. He supports the product definition and change management activities for updates to these models. Prior to RMS, Justin managed engineering and research projects focused on community resilience to earthquakes for GeoHazards International, and he has experience conducting site-specific seismic evaluations of existing buildings. Justin is a registered civil engineer in the state of California and holds a bachelor's degree in structural engineering from the University of California, San Diego, a master's degree in structural engineering from the University of California, Berkeley, and a post-graduate diploma from the London School of Journalism. Justin is a member of the Earthquake Engineering Research Institute.

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