The 1968 Casiguran earthquake occurred on with a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

of 7.6 and a maximum

Mercalli intensity The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

of IX (''Violent''). The thrust earthquake's epicenter was in Casiguran,

Quezon Quezon, officially the Province of Quezon ( tl, Lalawigan ng Quezon), is a province in the Philippines located in the Calabarzon region on Luzon. Kalilayan was the first known name of the province. It was later renamed Tayabas. In honor of the ...

(now part of

Aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

province). A small non-destructive tsunami was generated and at least 207 people were killed. The majority of the deaths occurred in the collapse of a six-story building in Manila.

Damage

Manila Manila ( , ; fil, Maynila, ), officially the City of Manila ( fil, Lungsod ng Maynila, ), is the capital of the Philippines, and its second-most populous city. It is highly urbanized and, as of 2019, was the world's most densely populated ...

, many structures that suffered severe damage had been built near the mouth of the Pasig River on huge

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

deposits. A number of buildings were damaged beyond repair while others only suffered cosmetic damage. 268 people were reported to have died during the collapse of the six-story

Ruby Tower The Ruby Tower was a six-story building in Manila, Philippines, completed that collapsed on August 2, 1968, during the Casiguran earthquake killing over 250 people. Background The building, constructed at a cost of $250,000, was located on the ...

, located at the corner of Doroteo Jose and Teodora Alonzo Streets in the district of Santa Cruz. The entire building, save for a portion of the first and second floors at its northern end, was destroyed. Allegations of poor design and construction, as well as the use of poor-quality building materials arose. In the district of Santa Ana, one person was injured by debris from a damaged apartment building. Two more people from Aurora sub province and

Pampanga Pampanga, officially the Province of Pampanga ( pam, Lalawigan ning Pampanga; tl, Lalawigan ng Pampanga ), is a province in the Central Luzon region of the Philippines. Lying on the northern shore of Manila Bay, Pampanga is bordered by Tarlac ...

died as a direct result of the quake. Around the town of Casiguran, there were several reports of landslides, the most destructive one at Casiguran Bay.

Aftershocks

The aftershock sequence throughout the month of August included many moderate shocks, including fifteen over 5.0 . The strongest of these occurred on August 3 with a 5.9 event that produced intensities of III–IV in Manila.

Aftermath and legacy

The former location of Ruby Tower in Santa Cruz district is now a memorial hall which stands today.

Notes

References

Sources *

External links

Casiguran Earthquake - 02 August 1968
– Philippine Institute of Volcanology and Seismology
M7.6 - Luzon, Philippines
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...