1968 Casiguran Earthquake

Also known as: Ruby Tower Earthquake (popular usage)

Definition

The 1968 Casiguran Earthquake was a magnitude 7.3 earthquake that struck shortly after midnight on August 2, 1968, with its epicenter near Casiguran, Aurora, on the northeastern coast of Luzon. The shaking killed about 200 people, most of them when the six-storey Ruby Tower condominium in Binondo, Manila collapsed, making it one of the deadliest earthquakes in the modern history of Manila and a landmark case in Philippine earthquake engineering and building safety. (Wikipedia — 1968 Casiguran earthquake, Wikipedia — Casiguran, Aurora)

Identities

Source Type	Identity
Wikipedia	1968 Casiguran earthquake
Wikidata	1968 Casiguran earthquake (Q3161000)
DBpedia	N/A
ProductOntology	N/A
Wiktionary	N/A
Library of Congress Subject Headings (LCSH)	N/A
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NCBI Taxonomy	N/A
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Google Scholar	1968 Casiguran earthquake Ruby Tower collapse Manila seismic hazard Luzon
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OpenCyc	N/A

Also Known As

Ruby Tower Earthquake (popular usage)

Examples and Analogies

Distant-blast lesson: The earthquake is to Manila what the 1985 Mexico City earthquake was to that capital — a moderate-to-large event far from the city whose soft soils amplified shaking and felled specific buildings.
Engineering pivot: Ruby Tower’s collapse played the role in Philippine building regulation that damaged buildings in other countries played abroad, forcing engineers to confront design and construction deficiencies.

Usage Scenarios

1. Earthquake Engineering Case Study

The Ruby Tower collapse is studied for how soil conditions and structural weaknesses combined to concentrate fatalities in a single building.

2. Seismic Hazard Awareness

The event is cited in explaining that even distant epicenters can severely shake Metro Manila through the valley’s soft sediments.

3. Emergency Preparedness Planning

Commemoration and drills use the anniversary to promote midnight-scenario preparedness, when most residents are asleep indoors.

Strategies

Incorporate the Ruby Tower case in structural engineering curricula on irregular buildings and poor construction quality
Use the event’s long-distance effects to justify stringent design standards for high-rise construction on Manila’s reclaimed and alluvial soils
Anchor household earthquake plans on the scenario of a night event with blocked roads and disrupted power

Security and Safety Measures

Modern building codes with seismic detailing requirements exist precisely to prevent Ruby Tower-type progressive collapses
Rapid structural assessment teams after earthquakes tag buildings to prevent re-occupancy of unsafe structures
Emergency communications redundancy addresses the midnight-timing problem the 1968 event demonstrated

Historical Context

The earthquake struck at 12:11 a.m. on August 2, 1968, with its epicenter offshore near Casiguran, Aurora, then a remote northern Luzon town. Although Aurora felt the strongest shaking, the deadliest effect occurred more than 200 kilometers away: the Ruby Tower, a six-storey residential condominium on Doroteo Jose Street in Binondo, pancaked to the ground in seconds, killing the great majority of the roughly 200 victims, many of them Filipino-Chinese families. The collapse exposed deficiencies in design and construction supervision for mid-rise buildings, spurred improvements in the national structural code, and remains the reference earthquake for Manila’s seismic vulnerability until the 1990 Luzon earthquake took that role.

Challenges and Controversies

Accountability for Ruby Tower

Investigations into the collapse produced lasting grievances among victims’ families over whether design flaws, construction shortcuts, or both were ever fully adjudicated.

Recurring Vulnerability

Decades later, engineering audits continue to find mid-rise buildings in Manila with similar pre-code vulnerabilities, showing the 1968 lessons remain incompletely applied.