The 1998 Bahía de Caráquez earthquake occurred on August 4, 1998 at 13:59 local time (18:59 UTC). This earthquake was of magnitude M_w 7.2. The epicenter was located at 10 km north of Bahía de Caráquez

Bahía de Caráquez

La Villa de San Antonio de Caráquez, known simply as Bahía de Caráquez or Bahía, is a coastal city in the Ecuadorian province of Manabí. The city is located on a sandy peninsula on the country's western coast at the mouth of the Río Chone...

, about 190 km NNW of Guayaquil

Guayaquil

Guayaquil , officially Santiago de Guayaquil , is the largest and the most populous city in Ecuador,with about 2.3 million inhabitants in the city and nearly 3.1 million in the metropolitan area, as well as that nation's main port...

, and about 215 km W of Quito

Quito

San Francisco de Quito, most often called Quito , is the capital city of Ecuador in northwestern South America. It is located in north-central Ecuador in the Guayllabamba river basin, on the eastern slopes of Pichincha, an active stratovolcano in the Andes mountains...

, Ecuador

Ecuador

Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

. The intensity in Bahía de Caráquez reached MM VIII. In Bahía de Caráquez, electricity, telephone, and water services disrupted, and many buildings were damaged. It was felt strongly in Guayaquil and Quito and could be felt in much of Ecuador and in Cali

Calì

Calì, also written in English as Cali, is an Italian surname, widespread mainly in the Ionian side of Sicily.For the surname Calì is assumed the origin of the Greek word kalos , or from its Sanskrit root kali, "time."The surname refers to:...

, Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

. An M_w 5.4 foreshock

Foreshock

A foreshock is an earthquake that occurs before a larger seismic event and is related to it in both time and space. The designation of an earthquake as foreshock, mainshock or aftershock is only possible after the event....

 occurred 1 hour and 24 minutes before the main shock and hence alerted many people. The Nazca Plate

Nazca Plate

]The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction along the Peru-Chile Trench of the Nazca Plate under the South American Plate is largely responsible for the...

 is subducting beneath the South American Plate

South American Plate

The South American Plate is a continental tectonic plate which includes the continent of South America and also a sizeable region of the Atlantic Ocean seabed extending eastward to the Mid-Atlantic Ridge....

 near the Ecuadorian coast. This earthquake was a shallow thrust earthquake in this subduction zone.

Since March 1997, Guagua Pichincha, 12 km to the west of Quito, began a period of unrest. Since May 1998, a seismic swarm occurred at Guagua Pichincha. Three days after the Bahía de Caráquez earthquake, on August 7, 1998, a moderate phreatic eruption

Phreatic eruption

A phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...

occurred in Guagua Pichincha. Guagua Pichincha remained active in 1999, and in 2000 its activities became more moderate.