Author Archives: Justin Moresco

About 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.

Puebla Earthquake: New Insights from RMS Reconnaissance

On September 19, the Mw7.1 “Puebla” earthquake struck Mexico City and surrounding states, causing the most fatalities (369) and damage of any temblor since the Michoacán event in 1985. The Mexican government has not yet published overall economic or insured loss tallies, but six days after the earthquake RMS publicly released an estimate of economic property losses between US$4 billion to US$8 billion and no more than US$1.2 billion in insured property losses.

To better understand the impact of this event, RMS sent a reconnaissance team to the affected region from October 1 to October 6. The RMS team spent most of the trip surveying sites in Mexico City but also visited Cuernavaca, Puebla de Zaragoza, and other cities in the states of Morelos and Puebla that were closer to the epicenter than the capital (Figure 1). This blog shares some of the key observations made by the RMS team.

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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.

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Puebla Earthquake: Echoes of Michoacán

On the morning of Tuesday, September 19, people across Mexico had taken part in the annual national earthquake drill and other remembrance activities, to commemorate 32 years since the 1985 Mw8.0 Michoacán Earthquake. Michoacán was the most devastating earthquake in Mexico’s history, leaving at least 9,500 people dead and more than 100,000 homeless.

No one could have imagined at the time of these drills that a little more than two hours later, at precisely 1:14 pm local time (CDT), they’d be experiencing a real earthquake, the same day as Michoacán, as the Mw7.1 “Puebla” earthquake struck Mexico City and surrounding states. The improbable had become reality.

RMS estimates that the Puebla earthquake caused between US$4 billion and US$8 billion in economic property losses and as much as US$1.2 billion in insured property losses. This estimate accounts for shake-only losses to building, contents and business interruption, including the effects of liquefaction and landslides.

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Searching for Clues After the Ecuador Earthquake

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.

“San Andreas” – The Scientific Reality

San Andreas—a Hollywood action-adventure film set in California amid not one, but two magnitude 9+ earthquakes in quick succession and the destruction that follows—was released worldwide today. As the movie trailers made clear, this spectacle is meant to be a blockbuster: death-defying heroics, eye-popping explosions, and a sentimental father-daughter relationship. What the movie doesn’t have is a basis in scientific reality.

Are magnitude 9+ earthquakes possible on the San Andreas Fault?

Thanks to the recent publication of the third Uniform California Earthquake Rupture Forecast (UCERF3), which represents the latest model from the Working Group on California Earthquake Probabilities, an answer is readily available: no. The consensus among earth scientists is that the largest magnitude events expected on the San Andreas Fault system are around M8.3, forecast in UCERF3 to occur less frequently than about once every 1 million years. To put this in context, an asteroid with a diameter of 1,000 meters is expected to strike the Earth about once every 440,000 years. Magnitude 9+ earthquakes on the San Andreas are essentially impossible because the crustal fault zone isn’t long or deep enough to accumulate and release such enormous levels of energy.

My colleague Delphine Fitzenz, an earthquake scientist, in her work exploring UCERF3, has found that, ironically, the largest loss-causing event in California isn’t even on the San Andreas Fault, which passes about 50 km east of Los Angeles. Instead, the largest loss-causing event in California is one that spans the Elsinore Fault and runs up one of the blind thrusts, like the Compton or Puente Hills faults, that cuts directly below Los Angeles. But the title Elsinore + Puente Hills doesn’t evoke fear to the same degree as San Andreas.

Will skyscrapers disintegrate and topple over from very strong shaking?

Source: San Andreas Official Trailer 2

Short answer: No.

In a major California earthquake, some older buildings, such as those made of non-ductile reinforced concrete, that weren’t designed to modern building codes and that haven’t been retrofitted might collapse and many buildings (even newer ones) would be significantly damaged. But buildings would not disintegrate and topple over in the dramatic and sensational fashion seen in the movie trailers. California has one of the world’s strictest seismic building codes, with the first version published in the early part of the 20th century following the 1925 Santa Barbara Earthquake. The trailers’ collapse scenes are good examples of what happens when Hollywood drinks too much coffee.

A character played by Paul Giamatti says that people will feel shaking on the East Coast of the U.S. Is this possible?

First off, why is the movie’s scientist played by a goofy Paul Giamatti while the search-and-rescue character is played by the muscle-ridden actor Dwayne “The Rock” Johnson? I know earth scientists. A whole pack of them sit not far from my desk, and I promise you that besides big brains, these people have panache.

As to the question: even if we pretend that a M9+ earthquake were to occur in California, the shaking would not be felt on the East Coast, more than 4000 km away. California’s geologic features are such that they attenuate earthquake shaking over short distances. For example, the 1906 M7.8 San Francisco Earthquake, which ruptured 477 km of the San Andreas Fault, was only felt as far east as central Nevada.

Do earthquakes cause enormous cracks in the earth’s surface? 

Source: San Andreas Official Trailer 2

I think my colleague Emel Seyhan, a geotechnical engineer who specializes in engineering seismology, summed it up well when she described this crater from a trailer as “too long, too wide, and too deep” to be caused by an earthquake on the San Andreas Fault and like nothing she had ever seen in nature. San Andreas is a strike-slip fault; so shearing forces cause slip during an earthquake. One side of the fault grinds horizontally past the other side. But in this photo, the two sides have pulled apart, as if the Earth’s crust were in a tug-of-war and one side had just lost. This type of ground failure, where the cracks open at the surface, has been observed in earthquakes but is shallow and often due to the complexity of the fault system underneath. The magnitude of the ground failure in real instances, while impressive, is much less dramatic and typically less than a few meters wide. Tamer images would not have been so good for ticket sales.

Will a San Andreas earthquake cause a tsunami to strike San Francisco?

Source: San Andreas Official Trailer 2

San Andreas is a strike-slip fault, and the horizontal motion of these fault systems does not produce large tsunami. Instead, most destructive tsunami are generated by offshore subduction zones that displace huge amounts of water as a result of deformation of the sea floor when they rupture. That said, tsunami have been observed along California’s coast, triggered mostly by distant earthquakes and limited to a few meters or less. For example, the 2011 M9 Tohoku, Japan, earthquake was strong enough to generate tsunami waves that caused one death and more than $100 million in damages to 27 harbors statewide.

One of the largest tsunami threats to California’s northern coastline is from the Cascadia Subduction Zone, stretching from Cape Mendocino in northern California to Vancouver Island in British Colombia. In 1700, a massive Cascadia quake likely caused a 50-foot tsunami in parts of northern California, and scientists believe that the fault has produced 19 earthquakes in the 8.7-9.2 magnitude range over the past 10,000 years. Because Cascadia is just offshore California, many residents would have little warning time to evacuate.

I hope San Andreas prompts some viewers in earthquake-prone regions to take steps to prepare themselves, their families, and their communities for disasters. It wouldn’t be the first time that cinema has spurred social action. But any positive impact will likely be tempered because the movie’s producers played so fast and loose with reality. Viewers will figure this out. I wonder how much more powerful the movie would have been had it been based on a more realistic earthquake scenario, like the M7.8 rupture along the southernmost section of the San Andreas Fault developed for the Great Southern California ShakeOut. Were such an earthquake to occur, RMS estimates that it would cause close to 2,000 fatalities and some $150 billion in direct damage, as well as significant disruption due to fault offsets and secondary perils, including fire following, liquefaction, and landslide impacts. Now that’s truly frightening and should motivate Californians to prepare.