An earthquake registering 6.4 Ms struck near Ambato, Ecuador, killing 5,050 people.

The 1949 Ambato earthquake was a magnitude 6.4 M_s earthquake that on August 5, 1949, struck Ecuador's Tungurahua Province southeast of its capital Ambato and killed 5,050 people. The nearby villages of Guano, Patate, Pelileo, and Pillaro were destroyed, and the city of Ambato suffered heavy damage. The earthquake flattened buildings and subsequent landslides caused damage throughout the Tungurahua, Chimborazo, and Cotopaxi Provinces. It disrupted water mains and communication lines and opened a fissure into which the small town of Libertad sank. Moderate shaking from the event extended as far away as Quito and Guayaquil.

The surface wave magnitude scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This magnitude scale is related to the local magnitude scale proposed by Charles Francis Richter in 1935, with modifications from both Richter and Beno Gutenberg throughout the 1940s and 1950s. It is currently used in People's Republic of China as a national standard for categorising earthquakes.

The successful development of the local-magnitude scale encouraged Gutenberg and Richter to develop magnitude scales based on teleseismic observations of earthquakes. Two scales were developed, one based on surface waves, , and one on body waves, . Surface waves with a period near 20 s generally produce the largest amplitudes on a standard long-period seismograph, and so the amplitude of these waves is used to determine , using an equation similar to that used for .

Ambato is a city located in the central Andean valley of Ecuador. Lying on the banks of the Ambato River, the city also sits beneath several tall mountains. It is the capital city of the Tungurahua Province, situated at an elevation of 2,577 meters above sea level. It is variously nicknamed "City of Flowers and Fruits", "Land of the Three Juans", and "Garden of Ecuador." Ambato's inhabitants are called Ambateños or Guaytambos. The current mayor of Ambato is Diana Caiza.