Trick-or-treaters and costumed revelers in the Gold Coast beaches of Costa Rica were shaken up by a 4.2 MW earthquake, which was felt in the communities of Santa Cruz, Nicoya, Cerro Negro, Diria, Nambi, Playa Samara, Playa Grande, Hojancha, and Playas del Coco. The epicenter was located inland, about 9 km south of Diria, between Liberia and the Nicoya peninsula, at a depth of 30.5 km.

The quake was detected by seismographs of the National Seismology Network (Spanish initials: RSN) of the University of Costa Rica ,and also by the Observatory on Seismicity and Volcanology (Spanish acronym: OVSICORI) of the National University. The temblor occurred at 6:48 pm, just a couple of hours after President Luis Guillermo Solis wrapped up his visit of the Turrialba Volcano region, which is still under yellow alert conditions and scenic flight restrictions due to the constant eruptions that have taken place since Wednesday night.

In the Tilaran region of Guanacaste, residents reported hearing Earth noises seconds before the short quake. Such noise reports often come from communities located close to active volcanoes, even when temblors are caused by a subduction process and not by volcanic activities. In the case of Tilaran, residents are probably anxious due to their proximity to the Arenal Volcano, which is active but not under alert such as the Poas, Rincon de la Vieja (Old Lady’s Corner) and the Turrialba.

Although Costa Rica is known as a nation where seismicity and volcanic activity are reported almost daily, residents have had their fair share of geological events in the last few weeks.

Halloween is not widely celebrated in this constitutionally Catholic nation; the exception to this rule occurs in expat communities where North American families dress up and take their children door-to-door for the trick-or-treat custom. On this Halloween night, the earthquake was both a trick and treat in the sense that it was not strong enough to cause damage or injury, but it did manage to scare quite a few people.