Introduction
On October 30, 2023, an earthquake with preliminary magnitude of 5.6, struck Jamaica with an epicenter located approximately 10km south of Portland. (The Earthquake Unit of Jamaica|Retrieved October 30, 2023).
This most recent event mark as the 3rd (minimum) earthquake with an epicenter on Jamaica mainland, at a magnitude of 4.90 and above, in 2023. The 1st earthquake of 4.90 took place on April 15, 2023 (epicenter in St. Thomas). And the 2nd earthquake with a magnitude of 4.90 took place in Portland (epicenter near Hope Bay), in September, 2023. (Source: The Earthquake Unit of Jamaica).
Cracking of Residential, Schools Government, Private-Commercial & Hospital Buildings; Mass Movement; Shock & Trauma: Outcomes of These Earthquakes
Damage of buildings, including: Schools, Universities, Government, Private-Commercial & Hospitals in the aftermath of the October 30, 2023 main earthquake in Jamaica (predominantly within eastern parishes), can be seen in viral images & videos, on multiple social media platforms. Some of these can be seen below.
Source: Nationwide News Network
3 Storey House Collapse-Portland, Jamaica. Source: Unknown.
Earthquake-Induced Rockfall. Location in Jamaica-Unknown. Source: Unknown.
Minor Cracks to UWI Medical Science Building. Source: OB Fitness
Damage to Building (unconfirmed-Taylor Hall, UWI Mona). Source: Unknown.
Damage to a building in Down Town Kingston (unconfirmed). Source: Unknown.
Cases of Children Hospitalized as a Reult of the Earthquake
While listening to midday RJR news (October 30, 2023), reports of groups of children turning up at hospital(s) due to physical injuries associated with the earthquake, as well as truma was heard by the author.
Many entities closed early in the aftermath of the October 30, magnitude 5+ earthquake, in order to assess structural damages of buildings, as well as to conduct other post-earthquake event assessments.
Jamaica’s Outcome of the felt October 30, 2023 earthquake was minor according to The Prime Minister of Jamaica. Was It?
Relative to Haiti’s magnitude 5+ earthquake in January 2023, that resulted in damages of many buildings in Jèrémie & Sainte Hèlène. (See Jamaica Observer Article for reference; retrieved October 31, 2023). The Prime Minister of Jamaica’s statements, of Jamaica having minor damages (caused by the October 30, 2023 earthquake), does hold some weight.
But with this October 30, 2023 earthquake, and what appears to be a relative year-on-year increasing in the number of felt earthquakes (magnitude 4 and above), with an epicenter on Jamaica mainland, since 2020, Jamaica & Jamaicans must be alert & prepared; and start doing their continuous collective parts-individual (household), community, parish, national- towards mitigating current & future short term damage(s) to themselves, loved ones and overall interests.
Why?
Because among other things, these minor-moderate earthquakes are weakening the: buildings, slopes, and bedrock resistance capacity, thus supporting relatively greater chance of failure (slope, subsidence/sinking, damage to building), within relatively short-medium terms (whether we get struck by a magnitude 6.5+ or not).
Given that the bulk of these relatively increasing magnitude & intensity (since 2020) are concentrated in the eastern end of Jamaica; and this end of the country is where the Kingston Metropolitan Area is located; and this is also where a high concentration of the country’s population reside (Kingston, St. Andrew, St. Catherine), the chance of increasing damage to buildings, housing this population, goes up.
Read: Geohazards| Geo-events| Geology| And You.
Think of the Minor Damage to Buildings as Weathering to Rock Formations/Rocks In Soil in Natural Environment
In the natural environment the rocks in situ (not moved) undergo breakdown. This breakdown is controlled by:
- Temperature.
- Moisture.
- Mineral-make up of the rocks.
- Bio-agents (roots of trees, burrowing animals…)
Etc.
The rocks that are exposed to relatively warm temperatures, moisture & bio-disturbance (natural & non-natural), breakdown faster, relative to rocks in dry, and/or cold environments. Countries located in tropical climatic zones, such as Jamaica, Haiti, Trinidad and the Lesser Antilles, experience relatively faster weathering of their rocks (geology). When you combine weathered rock (weakened) with a tremor (earthquake), the chance of failure, or scale of rock failure (bedrock/slope), also increases.
Concrete As Building Material; Have Engineers & Geologists Assess
Given that a dominant building material (residential & commercial) in Jamaica is concrete (calcium carbonate), the buildings we live in & work in, are also experiencing weathering. Signs of this weathering prior to an earthquake can be observed as surface cracks on the building. While these cracks may not be deep enough to be considered for structural intervention at the initial stage; as a ‘slow creeper’, these cracks can set the stage for increased damage to buildings & eventual rock fall (hazard to people in and around buildings), during an earthquake (high magnitude-low felt magnitude).
With this being said, if you observe cracks on your building, and even if you don’t, seek to have your building & overall foundation (including bedrock/ site geology) assessed & addressed by a Professional Engineer (civil, structural, geotechnical), and Geologist, post a felt earthquake event.
The geologist with their deeper understanding of the earth’s geophysics; as well as layering of rocks- especially those in conjunction with: diferent rock types, water table & deformed rock–faults & folds (contact zones), can better interpret and inform of these inherent geologic considerations relevant to an engineering project, relative to an engineer alone.
About The Author
Oshane Bryant: BSc Geology, Geography Minor; ACE CPT since 2012; Jamaica Business Development Corporation (JBDC) Accelerator Graduate-2018 cohort; Licensed KUKIBO Martial Arts & Self Defense, Senior Instructor; OB Fitness Founder & Managing Director.