On Monday Evening a Significant M5.5 Earthquake struck near San José in Costa Rica.

Written by Earthquakelist.org on March 21st, 2023. Last updated May 19th, 2023.

In the evening of Monday March 20th, 2023, a significant M5.5 earthquake hit under land 63 kilometer from San José in Costa Rica. Around 5.9 million people have been exposed to shaking. Panama and Nicaragua are also near its epicenter.

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Earthquake Summary

The earthquake struck on land in Costa Rica, 63 kilometer (39 mi) south of San José. The center of this earthquake had a quite shallow depth of 35 km. Shallow earthquakes usually have a larger impact than earthquakes deep in the earth.

Date and Time:	Mar 20, 2023 07:44PM (Costa Rica Time) - Mar 21, 2023 01:44 Universal Time.
Location:	63 km south of San José, Costa Rica. Coordinates 9°22'6"N 84°6'31"W.
Map:	Map of area around epicenter. Click to open in Google Maps.
Magnitude:	MAG 5.5 Detected by 72 stations. Maximum Error Range ±0.037 .
Depth:	35 km (22 mi) A quite shallow depth.
Max. Intensity:	IV Light On the Modified Mercalli Scale.
Tsunami Risk:	Low tsunami risk Earthquakes under MAG-6.5 do not usually cause tsunami's. Always stay cautious - More info here.

Minimal impact predicted

Based on scientific estimates by the US Geographic Survey (USGS), the risk of high fatalities for this earthquake is classified at level GREEN (low). They expect an 65% likelyhood of between 0 and 1 fatalities, and a 96% chance that the number of fatalities falls no higher than 10.

The USGS classifies the economic impact of this earthquake at level GREEN (low). They expect an 65% likelyhood of between 0 and 1 million US Dollars in economic damage and impact, and a 96% chance that the economic impact of this earthquake falls no higher than 10 million USD.

Roughly 5.9 million people exposed to shaking

This earthquake may have been felt by around 5.9 million people. That is the expected population size of the area exposed to a level of shaking of II or higher on the Modified Mercalli scale according to the USGS.

An estimated 209,300 people were exposed to level IV. At this level, light shaking and likely no damage can be expected. Intensity level III was experienced by the majority of people (around 5.6 million). In their region, weak shaking and probably no damage can be expected.

People in 3 countries have been exposed to shaking. In Costa Rica , around 5.2 million people, with impact levels up to IV (light shaking, likely no damage). In Panama , around 640 thousand people. In Nicaragua, shaking was experienced too.

Nearby towns and cities

Costa Rica , Panama and Nicaragua are all located within 300km distance of the epicenter of the earthquake.

The closest significant population center near the earthquake is Tejar in San José, Costa Rica. Tejar is located 44 kilometer (27 mi) south-southeast of the epicenter. The intensity of shaking and damage in Tejar is estimated to be around level IV on the Modified Mercalli Intensity scale (light shaking, likely no damage).

A complete list of nearby places is included below. Estimated intensity data (MMI) sourced from a shake-map published by the US Geographic Survey is shown where available (cities without data probably experienced little impact).

Overview of nearby places

Earthquake Intensity Map

The graph below overlays a map of the region around the epicenter with earthquake intensity data provided by the US Geographic Survey. The highest intensity level detected for this earthquake is IV.

I Not felt

II Weak

III Weak

IV Light

V Moderate

VI Strong

VII Very Strong

VIII Severe

IX Violent

X Extreme

Shaking reported by 103 people in 3 countries

People that feel an earthquake may report their experience to the US Geographic Survey. Currently, 103 people have reported shaking in 34 places in 3 countries (Nicaragua, Panama, Costa Rica).We keep updating this article as more ground reports become available. You may report that you felt this earthquake here.

Places with most reports:

• Quepos, Puntarenas, Costa Rica: 21 people.
• San Isidro (San Isidro de El General), San José, Costa Rica: 13 people.
• Jacó, Puntarenas, Costa Rica: 13 people.
• Palmares, Alajuela, Costa Rica: 7 people.
• Atenas, Alajuela, Costa Rica: 5 people.
• San Rafael, San José, Costa Rica: 4 people.
• Puerto Cortés, Puntarenas, Costa Rica: 3 people.
• San Pedro, San José, Costa Rica: 3 people.
• Mercedes, San José, Costa Rica: 2 people.
• Barranco, Bocas del Toro, Panama: 2 people.

8 Aftershocks detected

Since this main shock, 8 smaller aftershocks were detected. A 4.2 magnitude earthquake hit 1 day later 17 km (11 mi) southwest of this earthquake.

Before this earthquake struck, 4 smaller foreshocks occurred. Roughly 4 hrs before this earthquake, a foreshock measuring MAG-3.3 was detected nearby this earthquake.

Overview of foreshocks and aftershocks

More earthquakes coming?

Aftershocks are usually at least 1 order of magnitude less strong than main shocks. The more time passes, the smaller the chance and likely strength of any potential aftershocks.

In only six percent of cases, significant earthquakes are followed by a larger main shock, making the current earthquake a foreshock. While the chance of this happening is not so large, it is adviced to maintain cautiousness in the hours and days following a major earthquake.

Earthquakes like this happen often in the region

Earthquakes of this strength are very common in the region. This is the strongest earthquake to hit since October 20th, 2022, when a 6.7 magnitude earthquake hit 270 km (168 mi) further south-east. That was also the heaviest earthquake to hit the region in the past 10 years.

In total, 16 earthquakes with a magnitude of 5.5 or higher have been registered within 300km (186 mi) of this epicenter in the past 10 years. This comes down to an average of once every 8 months.

Low tsunami risk

Based on early data it appears this earthquake was not strong enough (lower than MAG-6.5) to be likely to cause destructive tsunami's. However this earthquake appeared to have hit at a shallow depth under sea, so stay cautious and monitor advice from local authorities.

Tsunami Risk Factors

Sources

Last updated 19/05/23 10:57 (). This article contains currently available information about the earthquake and is automatically composed. We continue to update this article up to a few days after the earthquake occurred.

1. US Geographic Society (USGS): Earthquake us7000jlkb
2. European-Mediterranean Seismological Centre (EMSC): Earthquake 20230321_0000021
3. Geonames.org: World Cities Database
4. Google Maps: Static API
5. Earthquakelist.org: Historic Earthquakes Database

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