- 2 days ago
Nature disaster
Category
đź—ž
NewsTranscript
00:00The strongest earthquake to hit the Philippines in 36 years struck offshore southern Mindanao this morning at 737 local time.
00:10The footage is striking, buildings cracked, walls came down, students ran out of classrooms in Davao del Sur, an airport
00:18closed in General Santos.
00:20Tsunami waves crossed three countries within hours, and the magnitude was revised upward within hours.
00:26From 7.0 in the first bulletin to 7.8 by mid-morning.
00:32The depth was 33 kilometers.
00:34The source, the Cotabato Trench.
00:37Intensity 7 in General Santos.
00:39Intensity 8 in Malapatan, Sarangani.
00:433.6 million people exposed to shaking strong enough to damage buildings.
00:4816 dead.
00:49More than 200 injured.
00:51A bridge with cracks.
00:52A school building collapsed.
00:5417 domestic flights canceled.
00:57Power knocked out across the south.
00:59And the tsunami did not stay theoretical.
01:021 meter in Sultan Kutarat.
01:041 meter in Sarangani.
01:061.4 meters in Kiamba.
01:0883 centimeters in Sulawesi, Indonesia.
01:11Smaller signals in Taiwan, Palau, southern Japan.
01:15Nine Philippine provinces evacuated their coasts.
01:18It is no longer a question of whether the Cotabato Trench can produce a tsunami.
01:23It already did.
01:25This is the same trench that produced the Moro Gulf earthquake on August 17, 1976.
01:32That earthquake measured magnitude 8.1.
01:35The tsunami that followed killed 8,000 people.
01:39Most of them while still asleep remains the deadliest natural disaster in modern Philippine history.
01:45It is no longer just a fault on a map.
01:49It is a structure with a body count.
01:51But here is the detail that tells the real story.
01:55FIVOLCS, the Philippine Institute of Volcanology and Seismology, has been watching this trench for seven decades.
02:02They have seismometers across Luzon, Visayas, and Mindanao.
02:07They have ocean-tide gauges on every Philippine coastline.
02:10They have a real-time link to the Pacific Tsunami Warning Center.
02:15They have issued tsunami warnings before.
02:18They have evacuated coastal provinces before.
02:21They have revised magnitudes upward before.
02:24And within hours, the chief of their seismology division identified the source by name.
02:29This is the structure responsible for the 1976 Moro Gulf earthquake and tsunami.
02:37The students at Matanao National High School in Davao del Sur,
02:41already outside for the morning flag-raising ceremony,
02:44who watched a school building collapse behind them.
02:48The families in General Santos, who walked out into the street while the walls of their houses kept moving.
02:55The coastal residents of Kiamba, Sarangani, who saw the sea recede before it returned at 1.4 meters.
03:02The air traffic controllers at General Santos International Airport, who diverted 17 flights before noon.
03:10The doctors in the regional hospitals, reading the Department of Health crisis protocol,
03:16while the floors were still shaking.
03:19They have all been doing the same thing.
03:21Moving away from the buildings, and watching the line of the coast.
03:26For 50 years, the Cotabato Trench has been quiet on this scale.
03:30The pattern held.
03:32The question now is whether the next 24 hours of aftershocks are the end of the sequence,
03:39or only the beginning of one the southern Philippines has not seen in half a century.
03:43This is how it happened.
03:46At 7.37 and 41 seconds local time, the seafloor offshore Sarangani ruptured.
03:52The first seismic waves reached General Santos in seconds.
03:56Within minutes, FIVOLCS issued a tsunami warning for nine coastal provinces.
04:01The first wave arrival window was set between 7.37 and 9.37 the same morning.
04:08The Pacific Tsunami Warning Center issued advisories for the Philippines, Indonesia, Palau, Taiwan, Japan, and Papua New Guinea.
04:17The initial magnitude estimate was 7.0.
04:21Within hours, FIVOLCS revised it to 7.8.
04:25The first waves arrived within the predicted window.
04:27One meter in Sultan Kutarat and Sarangani.
04:311.4 meters in Kiamba.
04:3483 centimeters in Sulawesi.
04:36In General Santos, the international airport closed and 17 domestic flights were canceled.
04:43A key bridge was flagged with structural cracks.
04:46Buildings partially collapsed.
04:48In Devo del Sur, abandoned school building at Matanao National High School came down.
04:54The students and teachers were already outside for the morning flag raising ceremony.
05:01The Department of Health activated its crisis protocol.
05:05President Marcos addressed the nation and told coastal residents to move to higher ground without waiting.
05:12The Pacific Tsunami Warning Center lifted the immediate threat approximately five hours after the quake.
05:18But the aftershocks have not stopped.
05:21What the seafloor did this morning was three things at once.
05:25A fault that broke.
05:26A seafloor that moved.
05:28A column of water that lifted.
05:30The Cotabato Trench is a subduction zone.
05:33The Sunda Plate and the Philippine Sea Plate converge here at approximately 7 to 10 centimeters a year.
05:40Most of the time, the two plates lock against each other.
05:44The stress builds.
05:45The locking holds.
05:46For decades.
05:47For generations.
05:49Until it does not.
05:50When a section of the trench releases that stress, the seafloor moves vertically in seconds.
05:56The vertical motion pushes the entire water column above it.
06:00The push spreads outward as concentric waves.
06:02That is the tsunami.
06:04Rupture.
06:05The official term for what happened along the Cotabato Trench at 737 this morning.
06:11A fault surface.
06:13Tens of kilometers long.
06:15Breaking in seconds.
06:16Releasing energy that had been stored for 50 years.
06:20Unlike Mayon's slow disgorgement of magma along the Miisi gully.
06:24This was sudden.
06:26Unlike a volcanic earthquake.
06:27Magma forcing its way through rock.
06:30This was tectonic.
06:31Unlike Mayon's daily bulletins for 155 consecutive days.
06:36This was 12 seconds of motion the entire southern Philippines felt at once.
06:42When the seafloor lifted, the water had to go somewhere.
06:46It went outward.
06:47The first wave reached Kiamba at 1.4 meters.
06:51The same energy reached Sulawesi at 83 centimeters.
06:55The same energy reached southern Japan as a smaller signal.
06:59The Pacific had moved.
07:00That is what the gauges along the western Pacific were reading.
07:05While the buildings in General Santos were still settling.
07:09To understand what is actually happening under the surface.
07:13Look at the structure that just moved.
07:15The Philippines sits on the Pacific Ring of Fire.
07:19The most seismically active region on earth.
07:22The Cotabato Trench runs along the southern coast of Mindanao.
07:26The convergence between the Sunda Plate and the Philippine Sea Plate here is not clean.
07:32It's oblique.
07:33Part of it is taken up by subduction along the trench.
07:36Part of it is taken up by strike-slip faults.
07:39The Philippine Fault Zone and Cotabato Fault System.
07:43The trench is a place where stress accumulates for decades at a time.
07:48Until it does not.
07:49Here is what is not making most headlines.
07:52On August 17th, 1976, the same Cotabato Trench ruptured.
07:58The magnitude was 8.1.
08:00The earthquake itself caused damage across western Mindanao.
08:04But the tsunami that followed was the killer.
08:07The waves swept the Moro Gulf Coast in the pre-dawn darkness.
08:12Most of the people who died never woke up.
08:158,000 people were killed.
08:16Entire coastal villages were erased from the map.
08:20It remains the deadliest natural disaster in modern Philippine history.
08:25Fivolks named the same trench within hours of this morning's earthquake.
08:30The difference today is that the magnitude was lower.
08:337.8 instead of 8.1.
08:37The waves were smaller.
08:38A meter and a half instead of several meters.
08:41The warning was faster.
08:43Most people moved before the sea did.
08:45The similarity today is that the structure that produced 8,000 deaths in 1976
08:52is the same structure that just produced 1.4 meters of tsunami in Kiamba.
08:5850 years apart.
08:59Same trench.
09:00Same coast.
09:01And it is still not over.
09:02The Pacific Tsunami Warning Center has lifted the immediate threat.
09:07But Fivolks has not declared the sequence finished.
09:11They have not ruled out aftershocks above magnitude 6.
09:15They have not reopened the bridges flagged with structural cracks.
09:19The ground is still moving.
09:21The airport is still closed.
09:23The hospitals are still triaging.
09:26The damaged buildings are still being assessed.
09:29The question is not whether the Katabato Trench can produce a deadly tsunami.
09:34It did.
09:3550 years ago.
09:36And the proof is in the death toll.
09:38The question is not whether this morning's earthquake was real.
09:42The waves were measured.
09:43The buildings collapsed.
09:45The question is what the residents of Sarangani, General Santos, Sultan Kutarat, and Davao Occidental, and the coastal towns of
09:53Sulawesi, Palau, southern Japan, do in the next 24 hours.
09:58As the same trench that killed 8,000 half a century ago decides whether this morning was the whole story
10:06or only the start of it.
10:07The Moro Gulf Coast still remembers 1976 as a warning.
10:12The land shook.
10:13The sea moved.
10:15The trench that killed 8,000 in 1976 is still there.
10:20If this story is worth telling, subscribe.
10:23We cover more of these every week.
Comments