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Massive 8.3 Quake Rocks Chile Triggers Tsunamis

17 Sep 2015, 1:04 am

Chile Quake 2



Update: 3:00am local time(8/17/14) One million people are on the streets seeking refuge:

Update: 8:15pm ET (8/16/15)–The USGS is now showing five aftershocks, all occurring within 50 minutes of the original quake.

Currently at least 5 are confirmed dead after A strong 8.3 earthquake struck off Chile’s coast on Wednesday.

(#NOW: New from Chilean Government Number of dead confirmed at 5. There’s a million evacuees …)

The Quake

Image: USGS
(Image: USGS)

According to the USGS: The September 16, 2015 M 8.3 earthquake west of Illapel, Chile, occurred as the result of thrust faulting on the interface between the Nazca and South America plates in Central Chile. At the latitude of this event, the Nazca plate is moving towards the east-northeast at a velocity of 74 mm/yr with respect to South America, and begins its subduction beneath the continent at the Peru-Chile Trench, 85 km to the west of the September 16 earthquake. The size, location, depth and mechanism of this event are all consistent with its occurrence on the megathrust interface in this region.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Events of the size of the September 16, 2015 earthquake are typically about 230×100 km in size (length x width).

Chile has a long history of massive earthquakes, including the 2010 M 8.8 Maule earthquake in central Chile, which ruptured a ~400 km long section of the plate boundary south of this 2015 event (and to the south of the Juan Fernandez Ridge, which enters the trench immediately south of the 2015 earthquake). This subducton zone also hosted the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile. Over the century prior to the September 16, 2015 earthquake, the region within 400 km of this event has hosted 15 other M 7+ earthquakes.

Tsunami in Chile
Tsunami Watch

The quake triggering a tsunami alert and coastal evacuations. NOAA’s Pacific Tsunami Warning Center has predicted wave heights exceeding 36 feet along the Chilean coast.

(“We call for evacuees to stay on high ground”)

Tsunami advisories have also been issued for:
Hawaii–

Based on all available data a major tsunami is not expected to strike the state of Hawaii. However, Sea level changes and strong currents may occur along all coasts that could be a hazard to swimmers and boaters as well as to persons near the shore at beaches and in harbors and marinas. The threat may continue for several hours after the initial wave arrival.

The estimated time of arrival of the initial wave is: 3:11 am HST – Thursday (9/17/2015)

California–

According to the NOAA Advisory: “If you are located in this coastal area move off the beach and out of harbors and marinas.” The advisory included coastal areas from San Diego County to Ragged Point, about 50 miles north of San Luis Obispo.

Other areas Include–

Pacific-facing coasts could see waves of more than 3 feet above the tide line, including Mexico, Russia, New Zealand and many other Pacific islands.

 

A Tsunami Warning means–

All coastal residents in the warning area who are near the beach or in low-lying regions should move immediately inland to higher ground and away from all harbors and inlets including those sheltered directly from the sea. Those feeling the earth shake, seeing unusual wave action, or the water level rising or receding may have only a few minutes before the tsunami arrival and should move immediately. Homes and small buildings are not designed to withstand tsunami impacts. Do not stay in these structures.

All residents within the warned area should be alert for instructions broadcast from their local civil authorities. A tsunami has been recorded.

A Tsunami Advisory means–

A tsunami capable of producing strong currents or waves dangerous to persons in or very near the water is expected. Significant, widespread inundation is not expected for areas under an advisory. Currents may be hazardous to swimmers, boats, and coastal structures and may continue for several hours after the initial wave arrival.

Images:
Quake & Aftershock–

Alarma de tusunami en Valparaíso

Posted by Oscar Cornejo Olivares on Wednesday, September 16, 2015

Waves–


(Headline image: @JuanMirandaB)

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