In a span of eight hours on Monday night and into early Tuesday, experts from the University of Costa Rica and the National University registered at least 23 temblors with epicenters located north of the province of Cartago, some 22 kilometers northeast of the Costa Rican capital.

Ronny Quintero, a seismologist at UNA’s Volcanological and Seismological Observatory of Costa Rica (OVSICORI) reported that the temblors originated on local faults west of Irazú Volcano’s main crater. Experts said they are not directly related to the volcano’s activity.

The first occurred at 8:19 p.m. with a magnitude of 3.1 and and an epicenter 10 kilometers northwest of Pacayas.

Several minor earthquakes with magnitudes ranging from 2.4 to 3.7 followed, mainly in areas north and east of Cartago in the cantons of Jiménez and Oreamuno. Most of the minor quakes went unnoticed by local residents.

The strongest, at magnitude-4.2, was registered at 8:50 p.m. with an epicenter 9 kilometers northeast of San Rafael de Oreamuno.

The most recent was reported at 7:09 a.m. on Tuesday with a magnitude of 2.4.

OVSICORI received reports from residents throughout the Central Valley who felt at least three of the temblors, but there has been no significant damage or injuries.