Thread: BREAKING: Magnitude 8.3 Earthquake Strikes Off Chile, Tsunami Watch For Hawaii

BREAKING: Magnitude 8.3 Earthquake Strikes Off Chile, Tsunami Watch For Hawaii


Massive Earthquake Rocks Chile; Tsunami Warning Issued For Hawaii

September 16, 2015 4:14 PM

(USGS)


SANTIAGO, Chile (AP) — A powerful earthquake shook Chile’s capital Wednesday night, causing buildings to sway and people to take refuge in the streets. Several strong aftershocks hits within minutes as tsunami alarms sounded in the port of Valparaiso and authorities issued a tsunami alert for the country’s entire coast.

The U.S. Geological Survey reported the quake had a preliminary magnitude of 7.9. Chilean authorities recorded it as 7.2.

U.S. officials said the quake struck just offshore in the Pacific at 7:54 p.m. and was centered about 141 miles (228 kilometers) north-northwest of Santiago. It said the quake was 4.8 miles (5 kilometers) below the surface.

Chile’s emergency office warned that big waves caused by the quake could hit the coast by 11 p.m.

WEST COAST TSUNAMI TRACKING:


Tsunami Alerts & Maps

http://sanfrancisco.cbslocal.com/201...e-rocks-chile/

How do these things get from 7.2 to 8.3? That's more than 10x the amplitude.

Originally Posted by Captainron

How do these things get from 7.2 to 8.3? That's more than 10x the amplitude.

The first estimate is usually done by one or 2 stations near the quake.
As more and more stations report in and compare data from further away they are usually adjusted up or down.

http://earthquake.usgs.gov/earthquak...eneral_summary


M8.3 - 54km W of Illapel, Chile

VIII
DYFI? VIII
ShakeMap ORANGE
PAGER
Location

Data Source US³

31.563°S 71.737°W depth=25.0 km (15.5 mi) View interactive map

Time

• 2015-09-16 22:54:32 (UTC)
• 2015-09-16 15:54:32 (UTC-07:00) in your timezone
• Times in other timezones

Nearby Cities

• 54km (34mi) W of Illapel, Chile
• 76km (47mi) WNW of Salamanca, Chile
• 109km (68mi) NNW of La Ligua, Chile
• 118km (73mi) SSW of Ovalle, Chile
• 233km (145mi) NNW of Santiago, Chile

Seismotectonics of South America (Nazca Plate Region)

The South American arc extends over 7,000 km, from the Chilean margin triple junction offshore of southern Chile to its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 65 mm/yr in the north. Although the rate of subduction varies little along the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America.

Most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 km resulting from both crustal and interplate deformation. Crustal earthquakes result from deformation and mountain building in the overriding South America plate and generate earthquakes as deep as approximately 50 km. Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates. Interplate earthquakes in this region are frequent and often large, and occur between the depths of approximately 10 and 60 km. Since 1900, numerous magnitude 8 or larger earthquakes have occurred on this subduction zone interface that were followed by devastating tsunamis, including the 1960 M9.5 earthquake in southern Chile, the largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 M8.5 earthquake near Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the 2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just north of the 1960 event.

Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting plate.

These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern Peru and southern Ecuador, with depths between 110 and 130 km. Most of these earthquakes occur adjacent to the bend in the coastline between Peru and Chile. The most recent large intermediate-depth earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.

Earthquakes can also be generated to depths greater than 600 km as a result of continued internal deformation of the subducting Nazca plate. Deep-focus earthquakes in South America are not observed from a depth range of approximately 300 to 500 km. Instead, deep earthquakes in this region occur at depths of 500 to 650 km and are concentrated into two zones: one that runs beneath the Peru-Brazil border and another that extends from central Bolivia to central Argentina. These earthquakes generally do not exhibit large magnitudes. An exception to this was the 1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake occurred at a depth of 631 km, which was until recently the largest deep-focus earthquake instrumentally recorded (superseded in May 2013 by a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was felt widely throughout South and North America.

Subduction of the Nazca plate is geometrically complex and impacts the geology and seismicity of the western edge of South America.

The intermediate-depth regions of the subducting Nazca plate can be segmented into five sections based on their angle of subduction beneath the South America plate. Three segments are characterized by steeply dipping subduction; the other two by near-horizontal subduction. The Nazca plate beneath northern Ecuador, southern Peru to northern Chile, and southern Chile descend into the mantle at angles of 25° to 30°. In contrast, the slab beneath southern Ecuador to central Peru, and under central Chile, is subducting at a shallow angle of approximately 10° or less. In these regions of “flat-slab” subduction, the Nazca plate moves horizontally for several hundred kilometers before continuing its descent into the mantle, and is shadowed by an extended zone of crustal seismicity in the overlying South America plate. Although the South America plate exhibits a chain of active volcanism resulting from the subduction and partial melting of the Nazca oceanic lithosphere along most of the arc, these regions of inferred shallow subduction correlate with an absence of volcanic activity.

More information on regional seismicity and tectonics

http://earthquake.usgs.gov/earthquak...eneral_summary

BREAKING NEWS
Large tsunami waves observed along the Chilean coast after earthquake, Pacific Tsunami Warning Center says.

Hawaii under tsunami watch after strong quake off Chile

UPDATED 2:34 PM HST Sep 16, 2015




HONOLULU —The Pacific Tsunami Warning center says a tsunami watch is issued for the state of Hawaii effective at 1:08 p.m. Wednesday.

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Click here to find out if you live in a tsunami evacuation zone.

A 8.3-magnitude earthquake struck off the coast of northern Chile just before 1 p.m. Hawaii time.

Scientists say a tsunami may have been generated by the earthquake that could be destructive on coastal areas even far from the epicenter.

An investigation is underway to determine if there is a tsunami threat to Hawaii.

If tsunami waves impact Hawaii, the estimated earliest arrive of the first tsunami wave is at 3:11 a.m. Thursday.

Hawaii could see waves reaching 0.3 to 1 meter above the tide level.

For travel safety tips for visitors to the islands, please visit the Hawaii Tourism Authority's Travel Smart Hawaii website.

The city says the Disaster Prep Workshop scheduled for 6:30 p.m. Wednesday at Waianae District Park will be rescheduled for next month.

http://www.kitv.com/news/hawaii-unde...chile/35312240

Originally Posted by JohnDoe2

The first estimate is usually done by one or 2 stations near the quake.
As more and more stations report in and compare data from further away they are usually adjusted up or down.

Glad you're up on the earthquake science, more than me. Up here we just figure when the big fault zone goes everything ends anyway so why plan ahead?

9/16/15

http://www.alipac.us/f19/california-...visory-323386/