Figure 1: Damage on Adobe Houses

RECENTS EARTHQUAKES AND NATURAL DISASTERS IN PERU Dr. Carlos ZAVALA Japan- Perú Center for Earthquake Engineering Research and Disaster Mitigation -CISMID Facultad de Ingeniería Civil Universidad Nacional de Ingeniería (UNI) Lima Perú Av. Tupac Amaru 1150 Sector T UNI Lima 25 Tel/Fax (511)4810170 1. SUMMARY This report presents a brief summary of recent earthquakes and natural disasters phenomena occurred in Peru. The presentation of Nazca Earthquake, with magnitude 6.3 Mb, which affected 75% of the buildings. Most of the failures occurred on adobe built structures. Also lifelines and facilities damage are reported. Also two recent earthquakes are presented: the Chuschi earthquake, an intra-plate earthquake, that destroyed almost 45% of houses in the small town of Chuschi, is presented. The Arequipa earthquake (the second more important city in Peru) where most of the damage occurred in old colonial temples is presented. Finally the effects of El Niño phenomena over Lima downtown and its surrounding areas is presented. 2. NAZCA EARTHQUAKE 2.1. General Information On November 12 th. 1996 at local time 11h59m.38.69s, an earthquake occurred in Nazca-Acari area, in the limit between Ica and Arequipa Departments in Southern Peru. The earthquake had a magnitude 6.3 Mb with coordinates 15.47º S and 75.94º W with focal depth of 46.0 Km. The Earthquake was associated with the subduction of Nazca plate and its origin located near to the seismic gap between the earthquake of August 24 1942 (Ms=8.3) and earthquake of October 3 rd. 1974. The sequence of aftershocks was in south direction. The seismic event was complex with at least two main events that occurs after 20 and 33 seconds after the beginning of the phenomena. 2.2 Damage in Buildings A great amount of adobe houses in downtown of Nazca city collapsed because the low tension strength and adherence between adobe and mortar. Samples of adobe shown that composition of sand lime-clay was 43.4% of fines, 22% of liquid limit, 16.7% on plastic limit and 5.4 of plasticity index. Also compression tests show a fragile behavior of blocks, taken from collapse buildings. The main failures are associated with the joints between walls and also the inefficient anchors producing vertical cracks after three or four brick lines. A big amount of buildings had light slab system, based on cane without any collar beam or anchor, producing a tension failure with flexion failure in many cases. Most of confined and unconfined masonry buildings had small damage concentrated mainly on partition and closing walls. A few amount had structural damage. In most of buildings built without any supervision of an engineer or technician, damage on some structural elements was found. Figure 1: Damage on Adobe Houses

Housing Housing buildings presented the more severe damage. According with CISMID survey, 75% of the housing were affected by the earthquake, with incidence on one floor adobe buildings (Figure 1). Masonry and concrete buildings presented damage on partition walls and mainly on non-structural elements, without any collapse reported in this kind of buildings. Table 1, presents level of damage according with the material, and also introduce the percentage of damage by material type. From all the cases, adobe housing were the most vulnerable during this earthquake. Table 1: Buildings Damage related with material type Material Number Percentage of Total Percentage by type of material No Damage Low Damage Severe Damage Collapse No diagnosis Adobe 196 75.0% 0.5% 20.4% 58.2% 11.2% 9.7% Masonry 30 11.6% 43.3% 0% 0% 0% 56.7% Concrete 24 9.2% 25.0% 25.0% 8.3% 0% 41.7% Mix 11 4.2% 0% 27.2% 36.4% 18.2% 18.2% TOTAL 261 100.0% School Buildings Figure 3: Damage on schools -Sequence of Short column A high percentage of school buildings were damaged because their architectural configuration and construction defects. In other cases a soil problem affected the structure because a seismic amplification appeared because the organic characteristics of the soil. Short columns problems and also inefficient seismic joints between pavilions produced extensive damages. However other schools like CE- Antonio Raimondi didn t have any cracks or structural damage. The reason in this case was the use of good structural configuration, enough seismic joints, and the inclusion of shear walls on the structural system. 2.3 Lifelines and Services Water and Sewage System: It was observed damage on water tanks built with concrete frames in city water supply and also on private installations. The downtown tank is a concrete structure with 450 m 3 of capacity. It was damaged on the beam-column joints and water supply was interrupted. After evaluation of CISMID it was recommended to use until 1/3 of its capacity. The main lines of water supply and sewage systems presented broken sections and losses.

Highways: There was some landslides of earth and rocks on some secondary roads. However Pan- American highway was not interrupted; only one landslide was reported on Curva Lopez zone (KM. 387). Bridges: On Yauca bridge, near Km 568 of Pan-American highway, there was damage of a pile and the central beam suffered a diagonal tension failure. It was reported a liquefaction on the surrounding areas of the bridge. Figure 4: Damage on Yauca bridge Hospitals and Health Centers The main hospital in Nazca presented damage on the hot water pipeline system, due to fence walls collapse that cut the pipeline. Also small cracks appeared in the zone of seismic joints. During the emergency the hospital continued working without interruption of its function. There was not report of any damage on health centers. Figure 5: CISMID 1995 Vulnerability map of Nazca City On Summer 1995, prior to the earthquake, an study of Vulnerability of Nazca city produced the map shown in Figure 5. In all the cases, damage was concentrated on the red zone of very high vulnerability, confirming the diagnosis. In the map, yellow zones describe high vulnerability.

3. CHUSCHI QUISPILLACTA EARTHQUAKE 3.1 General Information On Sunday October 31 st. 1999, at 8:27 am. an earthquake occurred inn Chuschi-Quispillacta (Ayacucho) 360 Km. South East from Lima in the Central Andes region. According with the Geophysical Institute of Peru (IGP), the Magnitude was 4.1 Mb and it was related with fault movements on the high Andes, where similar event occurred on November 10 th 1980. This earthquake was related with the compression process of the Andean Highlands, as a result of a collision with the plate. The earthquake epicenter was located 11 Km SW of the localities of Chuschi and Quispillacta. The focal mechanism correspond to an inverse fault with horizontal pressure oriented in ENE-WSW direction. 3.2 Damage in Buildings Figure 6: Housing damage on Chuschi On the localities of Chuschi and Quispillacta most of the buildings were made by adobe, quincha or non-conventional materials (Figure 6). On Chuschi the earthquake was felt very strong. Many of the houses built with adobe collapsed. According the local information approximately 30 persons were injured due to collapsed of walls or stones. The church of CanchaCancha presented damage on the roof and also visible cracks on walls; also the collapse of one house was reported. Because the most used construction material on Andean zones is adobe, a severe damage and collapse occurred in Chuschi and Quispillacta. Approximately 210 houses were destroyed and 1100 houses were damaged. Table 2 presents a resume of the damage reported on the Chuschi area. Table 2: Damage in Adobe Buildings - Chuschi Earthquake Adobe Buildings State Number of Houses Percentage No damage 30 2.7% Low damage 60 5.4% Severe damage 500 45.4% Collapse 210 19.3% No diagnosis 300 27.2% TOTAL 1100 100.0%

4. THE AREQUIPA EARTHQUAKE 4.1 General Information On Saturday April 3rd 1999 at 1:17 am local time, an earthquake of magnitude 6 Mb, occurred in Southern Peru. The epicenter was located 18km NW the locality of Camana in Arequipa. Regarding intensity, the influence area of the earthquake was approximately 90,000 Km2, and correspond to degree III (MM) on the intensity map developed by IGP, shown in Figure 7. The area had a maximum intensity approximately degree VI (MM) with orientation in the direction NW-SE and included the localities of Caraveli, Camana and Ocoña. According with the report of Characato Observatory, the earthquake had magnitude of 5,8 on Ritcher scale with 50 seconds of duration. Figure 7: Intensity distribution during Arequipa Earthquake 4.2 Damage in Buildings A number of 40 adobe houses were affected in Arequipa city, and also the structures of two catholic temples: San Francisco and Compañía de Jesús presented cracks on their front walls and roof failure on their main domes. Also in Camana, around 35% of the adobe houses suffered severe damage and a death was reported in Ocoña town. 4.3 Bridges and Highway Damage Transit interruption on Kilometers 917, 1041 and 1050 were reported due to some instability on the slopes, stones and landslides. Workers of the Ministry of Transportation moved to these places in order to clean the roads and reopen the pass of vehicles. After 20 hours, the transit was reopened on the highway. On bridges Puente de Siguas and Atico- Cerro de Arena, landslides were reported. 5. THE EFFECTS OF EL NIÑO PHENOMENA IN LIMA 5.1 Background The city of Lima is located on the coast, with very few rain during summer season (January to March) in a common year. Lima is known as a dry city. However in a return period from 6 to 16 years, El Niño Phenomena appears and causes the increase of temperature and also very strong rain. On a city with plane roofs and without drainage system on many areas, a high level of damage on facilities and housing will occurs.

5.2 Effects on Huaycoloro Area On Monday February 23rd 1998 at 6 a.m. El Niño Phenomena reappears after 11 years. The suburbs of San Juan de Lurigancho, Huachipa, Zarate and Campoy were affected with very extensive damage. In Jicamarca ravine, the flood and stones started fall down, reaching Ramiro Priale highway around 7:15 a.m. Ten houses were destroyed and the flood crossed the streets interrupting the transit of vehicles, as shown in Figure 8 (a). The flood reached Puente Piedra bridge at 11 a.m., which is very near Governmental Palace, with a water depth of 1.20 m. (Figure 8 (b)). This unusual phenomena produced one death, 200 injured, 36 destroyed houses and more than 1800 houses affected by the water. Figure 8: (a) Floods on highway (b) Water near Puente de Piedra bridge 6. CONCLUSIONS Asia Pacific region is always affected by earthquakes and other natural disasters. Three earthquakes were presented on this report. A policy of planning for natural disaster reduction is urgent on developing countries of the Pacific region. In 1995 Microzonification of Nazca city was developed by CISMID. City s Authorities received the diagnosis, however nobody implemented a policy of education and prevention on the city. As a result, 75 % of buildings were damaged, including schools. The 1999 Chuschi Quispillacta earthquake affected the farmers population. Almost all the adobe houses were damaged. Since 1997 the adobe is not recommended as a building material unless appropriate confining is provided. The next week after the earthquake, farmers population were rebuilding their houses in adobe. In this case authorities did not educate and prevent future disasters. Other natural phenomena like El Niño, affected cities like Lima, a city without rain. Recent studies show that it is necessary to relocate the areas exposed to floods. 7. REFERENCES El Sismo de Nazca 12/11/1996, Javier Pique, Reporte del CISMID-UNI, Lima Perú Microzonificación para la Prevención y Mitigación de Desastres de la Ciudad de Nazca, Pedro Huiman y Julio Kuroiwa, CISMID-UNI, 1996. Informe del Sismo de Nazca Instituto Geofísico del Perú (IGP), 1996. El Terremoto de Chusqui-Quispillacta Ayacucho 31/10/1999, Hernando Tavera, et.al Boletín Sociedad Geológica del Perú, IGP. Plan de Prevención y Mitigación ante el Fenómeno del Niño en la cuenca de la quebrada de Jicamarca Cecilia Peche Becerra y Nemesio Canelo, CISMID-UNI. El Sismo de Arequipa 3/4/1999, Hernando Tavera Instituto Geofísico del Perú (IGP).