M8.3 Chile Earthquake

Update 1 | Summary
Posting Date: September 21, 2015, 4:15:00 AM

AIR Worldwide estimates that industry insured losses from the M8.3 earthquake that struck Chile’s central coast near Illapel on September 16 will be between CLP 400 billion (USD 600 million) and CLP 600 billion (USD 900 million).

AIR’s loss estimates explicitly capture damage from ground shaking, tsunami, and liquefaction. Losses are dominated by shake damage in AIR’s scenarios, with a very small contribution from liquefaction. Tsunami damage contributes from 27% to 38% of total losses across the scenarios. Note that AIR’s estimates are based on assumptions about take-up rates in Chile (the percentage of properties actually insured against the earthquake peril), about which there is considerable uncertainty. The range in loss estimates reflect uncertainty in the slip distribution at the fault, modeled ground motion, tsunami inundation, and damage estimation.  Note that the assumed exchange rate is 1 CLP = 0.0015 USD.

ALERT subscribers can download scenarios for the event, in addition to similar stochastic event IDs and a Touchstone-ready shape file of the tsunami inundation footprint.

AIR's insured loss estimates reflect:

• Insured physical damage to onshore property (residential, commercial/industrial), both structures and their contents, and auto
• Direct business interruption losses

The loss estimates do not reflect:

• Losses to uninsured properties
• Losses to land
• Losses to infrastructure
• Indirect business interruption losses
• Loss adjustment expenses
• Losses from non-modeled perils, including fire-following and landslide
• Demand surge—the increase in costs of materials, services, and labor due to increased demand following a catastrophic event. Demand surge can be applied by AIR software users who want to account for this variable.

As more information regarding damage caused by the M8.3 earthquake and resulting tsunami that struck north-central Chile on September 16 becomes available, a clearer picture of the overall impact of the event is coming in to view. Authorities have stated that at least 12 people have died as a result of the quake, which was felt as far away as São Paulo, Brazil, more than 3,000 km away. Strong shaking was felt in Chile’s capital city of Santiago, the nation’s most populous city, where tall buildings swayed for up to three minutes.

The main shock, which was followed by several strong aftershocks, triggered a tsunami that was recorded in several countries. The tsunami produced waves up to 1 meter in height as far away as the Hawaiian Islands.

Coastal regions, which were experiencing an influx of visitors ahead of the Chilean Independence Day weekend, were evacuated upon issuance of tsunami warnings. More than 1 million people were affected by the evacuation order.

Reported Damage

According to ONEMI, the Chilean agency responsible for public safety and emergency response, more than 400 residential buildings have been destroyed; in addition to these, more than 700 residential buildings have sustained major damage.

The port city of Coquimbo reported the highest tsunami wave at nearly 5 meters; debris and fishing boats washed inland into the downtown area, where homes and businesses were inundated. A state of emergency was declared in the Coquimbo region, where the ports of Tongoy, Coquimbo, and Los Vilos were closed. The town of Illapel, located directly east of the quake’s epicenter, suffered the heaviest damage resulting from strong ground motion.

Chile is the world’s leading producer of copper, and several mines were affected by ground shaking caused by the quake. Los Pelambres, operated by Antofagasta Minerals, and Andina, operated by Codelco, were temporarily closed as geotechnical engineers assessed conditions once the shaking had subsided.

Regional Seismicity

The September 16 earthquake was the result of convergence between the Nazca and South American tectonic plates. Here, the Nazca plate plunges beneath the South American plate, forming a subduction zone. Active subduction zones are some of the most likely plate interfaces to generate quakes of catastrophic magnitude and also pose the greatest risk of triggering tsunamigenic tectonic events.

The 2010 M8.8 Maule earthquake released a significant amount of accumulated energy and reduced the seismic risk offshore of Santiago, but increased the risk along the northern segment of the subduction, including the segment that ruptured during this recent earthquake.

 

Locking pattern along the Nazca subduction interface, prior to the 2010 Maule earthquake. Red regions show highly locked areas, white regions are partially locked, and green regions are unlocked. The yellow boxes show the approximate locations of the 2015 M8.3 Illapel earthquake and the 2010 M8.8 Maule earthquake. (Source: AIR)

The rupture area and the slip distributions of the recent earthquake and that of the 2010 Maule earthquake suggest that a small part of the Nazca subduction zone south of the rupture area of this recent earthquake and north of the rupture area of the Maule earthquake did not rupture during these two earthquakes and should be at a higher state of stress, thus increasing the likelihood of a future earthquake. This segment of the Nazca plate has experienced partial or full ruptures during the 1906 M8.2 and 1985 M7.98 earthquakes and is capable of producing a M7.5 to M8.0 earthquake.

The location and magnitude of this earthquake are consistent with AIR’s recent seismicity model for this region. AIR’s time-dependent model for this region estimates a higher rupture probability for this type of earthquake compared to the corresponding time-independent estimate. The time-dependent model was constructed using GPS data and the most advanced physical modeling available. It incorporates the details of past historic earthquakes that are consistent with the state of locking of the subduction zone, and information on the accumulation and release of strain in this region during the past few hundred years. The preliminary results of the slip distribution from this earthquake are consistent with AIR's overall determination of the spatial distribution of locked areas based on AIR’s kinematic block model.

The AIR earthquake team has analyzed the available seismological data on the September 16 earthquake and has posted a range of scenarios on the Scenarios page. Because of the unique nature of every earthquake, it is recommended that clients use these simulated scenarios of the actual event, instead of similar events from the stochastic catalog of the AIR Earthquake Model for Chile. It should be understood, however, that considerable uncertainty still exists, both with respect to the event parameters and with take-up rates.

Update 1 | Downloads
Posting Date: September 21, 2015, 4:15:00 AM