Deep earthquake in Peru is felt along the length of South America: More to follow?

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Tiegan Hobbs, Ph.D., Postdoctoral Seismic Risk Scientist (@THobbsGeo)

A magnitude-8.0 quake shook deep below the Amazon Rainforest in Peru, causing extensive liquefaction and shaking from Colombia to Chile. 

Citation: Tiegan Hobbs (2019), Deep earthquake in Peru is felt along the length of South America: More to follow?, Temblor, http://doi.org/10.32858/temblor.024

 

A powerful Mw 8.0 earthquake shook Peru at 2:41 a.m. local time on Sunday, May 26, 2019, from an epicenter within the Reserva Nacional Pacaya-Samiria of the Amazon Rainforest. Although it was felt from Colombia to Chile, this deep event (about 110 kilometers) did not generate a tsunami and only two casualties have been reported (AP). At least 26 people are injured in Peru and Ecuador. Casualties were limited due to the remote location of the epicenter and the depth of the quake.

 

The 26 May 2019 M=8.0 event was slightly larger and about 440 kilometers to the southeast of a M=7.5 earthquake that occurred in Ecuador on 22 Feb 2019.
The 26 May 2019 M=8.0 event was slightly larger and about 440 kilometers to the southeast of a M=7.5 earthquake that occurred in Ecuador on 22 Feb 2019.

 

Damage and liquefaction expected in the Amazon

This map, produced by the United States Geological Survey, shows estimated Mercalli shaking intensity (colored contour lines from maximum of orange level VIII) and liquefaction probability (colored contours with maximum dark purple representing a greater than 20% chance of liquefaction).
This map, produced by the United States Geological Survey, shows estimated Mercalli shaking intensity (colored contour lines from maximum of orange level VIII) and liquefaction probability (colored contours with maximum dark purple representing a greater than 20% chance of liquefaction).

 

The United States Geological Survey (USGS) now routinely produces maps of probable landslide and liquefaction. According to the shaking and topography of the area, this event is predicted to cause widespread and/or severe liquefaction affecting approximately 74,000 people. It is not predicted to cause an extensive landslide, though aerial surveys showed at least one landslide in the jungle.

 

Road damage in the Cajamarca Region from Twitter (@Crisanris).
Road damage in the Cajamarca Region from Twitter (@Crisanris).

 

Peru resident Cristina Andrade (@crisanris) reported road damage due to ground displacements from this event and aerial photography shows a landslide in the lush jungles of this region (Reuters). Little information has emerged about the extent of the destruction, despite incoming footage from the firefighters of Peru (@BomberosPE) showing rubble lining the streets of Yurimaguas, the town nearest the epicenter, in Alto Amazonas. Emergency teams and politicians have been converging on the affected areas to lead the response.

 

Landslide as a result of Sunday’s earthquake, as reported to Reuters (@Univ_inenglish).
Landslide as a result of Sunday’s earthquake, as reported to Reuters (@Univ_inenglish).

 

Not the first deep earthquake in this area

Events like this one, which occur deep within Earth’s crust and rupture under extensional forces, are different than usual subduction zone earthquakes. This earthquake occurred entirely within the subducting Nazca Plate, which is being pulled apart as it is sucked deeper into Earth’s mantle. We call this type of earthquake an “intraplate event: occurring within the plate. More often, subduction zone earthquakes are “interplate” events, in which earthquakes occur on the boundary between two plates. These events, like the 2016 M=7.8 earthquake in Pedernales, Ecuador (http://temblor.net/earthquake-insights/ecuador-earthquakes-what-happened-and-what-is-next-986/), tend to be shallower and therefore are closer to population centers and the ocean floor. They’re thus more likely to cause tsunamis and significant damage.

 

This figure, modified from Leyton et al., 2009, shows the difference between interplate events, which occur between two plates, and intraplate events, like Sunday’s Mw 8.0 event in Peru.
This figure, modified from Leyton et al., 2009, shows the difference between interplate events, which occur between two plates, and intraplate events, like Sunday’s Mw 8.0 event in Peru.

 

Questions may arise as to whether Sunday’s Mw 8.0 earthquake in Peru was related to a February Mw 7.5 event in Ecuador. That event was also a deep, extensional intraplate quake. While these two earthquakes were very similar and happened within a few months of one another, they were upwards of 400 kilometers apart. Therefore, the static stress change from the February event was too small to have triggered Sunday’s event.

Sunday’s quake, like most deep earthquakes, is likely to be relatively depleted in aftershocks [e.g. Wiens & McGuire, 1995]. So far, no events with magnitude greater than 2.5 have been reported by the USGS for that area.

References

pic.twitter.com/miV5ak8Gf6

pic.twitter.com/3bFW9JqfE9

USGS Event Pages

https://earthquake.usgs.gov/earthquakes/eventpage/us60003sc0/executive

(https://earthquake.usgs.gov/earthquakes/eventpage/us60003sc0/ground-failure/summary

https://earthquake.usgs.gov/earthquakes/eventpage/us2000jlfv/executive

Leyton, F., Ruiz, J., Campos, J., & Kausel, E. (2009). Intraplate and interplate earthquakes in Chilean subduction zone: A theoretical and observational comparison. Physics of the Earth and Planetary interiors, 175(1-2), 37-46.

Wiens, D. A., & McGuire, J. J. (1995). The 1994 Bolivia and Tonga events: Fundamentally different types of deep earthquakes?. Geophysical research letters, 22(16), 2245-2248.

Other News Sources

https://www.eluniversal.com.mx/english/magnitude-8-earthquake-hits-peru (Reuters)

https://www.apnews.com/3b12f5abea604f19a5ad36d700d090b1 (AP)

 

  • Tiegan Hobbs

    Hi Robin – the road damage shown in this article is likely due to liquefaction/lateral spreading. This occurs when water-bearing soils are deformed during earthquake shaking, as a result of that water being mobilized. Basically it causes the ground to behave like a fluid for a short period of time, which can cause significant damage to rigid infrastructure like roads.

  • Robin Luethe

    thanks.