Strong earthquake in Peru

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A strong earthquake shook Southern Peru. Contrary to what we expected initially, the earthquake is more powerful than expected. Local press is reporting a number of collapsed houses in Arequipa, especially in Acari region. Landslides are also reported. The services of the Civil Defense have already started assessing the situation.

We will keep you updated if more news becomes available.

Update 19:14 UTC: Collapsed houses are reported from Acari and Caraveli area in Arequipa. More houses are damaged, schools were evacuated. Several landslides occurred, blocking and damaging roads. Also the Pan Americana is affected.

Update 17:33 UTC: Due to the increased Magnitude, the maximum MMI has also been increased to MMI VII = very strong shaking for the coastal part. Still no reason for us to expect major damage also because this part of the country has regular very strong subduction earthquakes.

Update 17:23 UTC: Local people are reporting panic in many cities like Camana, Castilla and Arequipa. This is normal but we do not see any reason to expect damage in these cities. A powerful earthquake like this lasts normally more than 20 seconds and is perceived as very strong, even if not dangerous for damage.

Update 17:21 UTC: GDACS has calculated that NO people are living within a radius of 10 km from the epicenter. Less than 100 people are living in between 10 and 20 km. Only 6800 people are living within a 50 km radius.

We are confident that only a radius of 20 km may have slight damage like cracks in walls, fallen roof tiles and plaster etc.

Update 17:09 UTC: This part of the coastal area is luckily sparsely populated. The nearest village / area is the Yauca district. The earthquake has been felt until Lima, the capital of Peru at a distance of more than 500 km. Generally we can say that the quake will have been felt all over Peru.

The maximum calculated theoretical shaking will be MMI VI, strong shaking in the direct coastal area. Based on the type of earthquake, normally subduction type of earthquake and the max. MMI, we do not expect serious damage from this earthquake.

Update 17:07 UTC: The Magnitude has now been decreased to M6.6, a substantial difference but the bad news is that the epicenter is now being located near the coast.

Update 17:02 UTC: The exact epicenter is still preliminary and unsure. The exact epicenter is important to determine what shaking will be felt on the coast. Despite the NO TSUNMI report from the PWTC, the local coat can still have strong currents and people will certainly keep away from the coastline.

Very strong earthquake at an uncertain distance from the coast.

NO DESTRUCTIVE WIDESPREAD TSUNAMI THREAT EXISTS BASED ON HISTORICAL EARTHQUAKE AND TSUNAMI DATA.

HOWEVER – EARTHQUAKES OF THIS SIZE SOMETIMES GENERATE LOCAL TSUNAMIS THAT CAN BE DESTRUCTIVE ALONG COASTS LOCATED WITHIN A HUNDRED KILOMETERS OF THE EARTHQUAKE EPICENTER. AUTHORITIES IN THE REGION OF THE EPICENTER SHOULD BE AWARE OF THIS POSSIBILITY AND TAKE APPROPRIATE ACTION.

2013-09-25 16:42:43 UTC
2013-09-25 11:42:43 UTC-05:00 at epicenter
2013-09-25 06:42:43 UTC-10:00 system time

Location

15.851°S 74.562°W depth=45.8km (28.5mi)

Nearby Cities

46km (29mi) S of Acari, Peru
91km (57mi) SE of Minas de Marcona, Peru
120km (75mi) SSE of Nazca, Peru
135km (84mi) SSW of Puquio, Peru
498km (309mi) SSE of Lima, Peru

Ethnography

Peru is one of only five countries in Latin America whom have large segments of pure Amerindians -where almost 35% of all Peruvians are Amerindian. Most of the Amerindian communities are found the southern Andes yet there is a large portion found in the southern and central coast due to the massive immigration of farmers from the southern Andean cities to Lima (this occurred 50 years ago due to terrorism. Cities with pure Amerindian communities are mainly those in the southern Andes such as Puno, Cusco, Apurimac, Ayacucho, Andahuaylas and Cerro de Pasco. There are also Amazon´s native Amerindian communities yet they are very small compared to the rest of the population. Most of the northern coast´s natives such as the tallanes, mochicas, chimues, tumpis and chachapoyas, were not Andean but originated from tribes that migrated from the Amazon, the llano and Central America.

Mestizos constitute most of the people at 45% of the whole Peruvian population. The term denotes people of mixed ancestry be it European with Amerindian blood (most of Peruvians) or that of a mixture with certain African ancestry added. Most of the mestizos resulting from Spanish-Amerindian mixture are found in the central and northern coast. The other large portion is found in two specific Andean regions, Cajamarca and Arequipa. We must remember that in the mestizo category (around 45% of the total Peruvian population) there is also a considerable portion composed of Zambos or the Mixture of Amerindian with blacks found most commonly in Ica and Morropon, and that of Mulatos or the Mixture of whites/creoles with blacks whom are most common in Lima, Trujillo, Chiclayo, Lambayeque, Piura and Tumbes.

Around 17% of the population is of unmixed European ancestry (including many the descendants of Spaniards), they are called criollos or creoles. There are also descendants of Italians, German, and Lebanese, etc. The majority of them live in Peru’s largest cities and those found in northern coast such as Trujillo, Chiclayo, Piura and Lima. Others live in Cajamarca, San Martin, Iquitos and Huanuco. In the south only Arequipa has an important proportion of Spanish descendants and other creole populations.

Around 2% of Peruvians are of pure African ancestry and most of them live in coastal cities found south of Lima such as that of the Ica Region, cities like Canete, Chincha, Ica, Nazca and Acari.

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, making it the largest deep-focus earthquake instrumentally recorded, 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.