- 2 days ago
Tragedy Philippines 8--6-26
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00:07المواطنة
00:08تتعلم
00:08تيشيخ المواطنة
00:12الطفل
00:13الثالث
00:13الثالث
00:18باتطالية
00:19تتعلم
00:20ت نشيخ
00:21انتظار السلطان على البعض.
00:23وبعد ذلك السلطان على الفقام الأستخدام المحلولات
00:27يحدث سوية البطولين في حال الغدات شخص الوطف الأميس والدرجة
00:31من النوم بإمكانك وأنَ plants يستطيعون جديد
00:33الآن.
00:34مرحباً في هذا المسيقro.
00:37وسجس، عصب الحلقة
00:39وشيهوهيا المالات المستقبل خطر المزيئ
00:42تحديد من شيء واحد من مشاهدة
00:43although الآن بإنزال الأسفاء
00:47هذه الحالية.
00:50that is exactly what we do here.
00:51The link is right below.
00:53The Philippines does NOT sit on one tectonic boundary.
00:56It sits on several, all converging at the same time.
00:59The Philippines Sea Plate moves roughly 90 mm
01:01إلى the West-North West every year.
01:04That sounds almost nothing.
01:06Multiply it by 40 million years
01:07and you have built every major mountain range in Southeast Asia.
01:10To the West,
01:11this plate dives beneath the Eurasian Plate along the Manila Trench.
01:14A scar in the ocean floor that drops to nearly 5,000 m
01:1816,400 feet in places.
01:20To the east of Mindanao,
01:22the Philippine Trench and the Cotobato Trench
01:24create a geological vise.
01:26The island is being compressed from multiple directions
01:28at the same time.
01:29Running through the middle of all of this is the Philippine Fault,
01:32a left lateral strike-slip structure
01:33stretching roughly 1,200 km
01:37746 miles
01:38through the archipelago.
01:39Strike-slip means the two sides of the fault
01:41move horizontally past each other, like two hands
01:43sliding in opposite directions.
01:45The San Andreas Fault in California
01:47works the same way, just mirrored.
01:49What makes the Philippine Fault different
01:50is how it interacts with both subduction zones
01:53flanking the archipelago simultaneously.
01:55It is not just cutting through the island chain.
01:57It is negotiating the rotational strain
01:59that builds up when a single plate
02:01is being consumed from two different sides at once.
02:04That negotiation failed this morning.
02:06The hypocenter,
02:07the actual point underground where the rock first fractured,
02:10sits at approximately
02:1110 km, 6.2 miles depth.
02:13That is shallow.
02:15Alarmingly shallow for an 8-plus event in this region.
02:17For reference,
02:19the 2004 Sumatra earthquake
02:21that triggered the Indian Ocean disaster
02:23ruptured at 30 km, 18.6 miles.
02:26The 2011 Tohoku earthquake that hit northeastern Japan
02:29broke at 29 km, 18 miles.
02:32Both produced catastrophic tsunamis.
02:35Both were nearly three times deeper
02:36than what ruptured under Mindanao this morning.
02:38Depth determines how efficiently
02:40the energy travels to the surface
02:41and into the water above.
02:43Think of it this way.
02:44Drop a stone into deep water from 1 meter below the surface.
02:47The ripple on top is small, dispersed,
02:50spread out by the water column above it.
02:52Now hold that stone just 2 cm below the surface
02:54and release it.
02:55The displacement is immediate and enormous.
02:57That is the physics of today's earthquake.
03:0010 km of rock between the rupture and the seafloor.
03:04The energy transferred into the water column directly, efficiently,
03:07and with almost nothing absorbing it on the way up.
03:10A tsunami warning was issued within minutes.
03:12That is not panic.
03:13That is seismology doing its job.
03:16Now I need to explain what a seismic gap is
03:18because this is the part of the story
03:20that the news coverage will miss
03:21and it is the most important context
03:23for understanding what happened today.
03:25A seismic gap is a section of a fault
03:28that has not ruptured in a long time.
03:30Decades.
03:30Sometimes centuries.
03:32The plates on either side are still moving.
03:34The stress is still accumulating.
03:35But no earthquakes are releasing it.
03:37The fault is locked,
03:38held together by friction
03:40while the tectonic forces loading it never stop.
03:42Seismic gaps are not quiet zones.
03:44They are charged zones.
03:46They are a geological spring compressed to maximum tension,
03:49held in place by nothing but friction.
03:51In 2019, a team of geophysicists
03:53using GPE's ground deformation data
03:55published an analysis of the Philippine fault in Mindanao.
03:58Their results showed that specific segments
04:01in the southern part of the fault were accumulating strain
04:03at rates consistent with eventual large magnitude failure.
04:07The phrase they used was
04:08late in the interseismic cycle.
04:11In plain language,
04:12this segment had been loading for a long time.
04:14The spring was near maximum compression.
04:16What ruptured this morning may have been exactly that segment.
04:19And here is what seismologists are analyzing right now in real time,
04:22as this video reaches you.
04:24Coulomb stress transfer.
04:26When a fault segment ruptures,
04:28it does not just release its own accumulated stress.
04:30It redistributes pressure across the surrounding fault system.
04:33The failed segment acts like a pressure valve.
04:36It relieves itself, but it pushes the load onto adjacent sections.
04:39Those sections which were already loaded receive an additional stress increment
04:42on top of what they were already holding.
04:44This is how large earthquakes trigger aftershocks.
04:47And sometimes, how they trigger separate large earthquakes on nearby faults.
04:50Following a moment magnitude 8.2 rupture,
04:53seismological models consistently show elevated probability of magnitude 6 and above aftershocks lasting weeks.
05:00The probability of a 7 or higher event in the first month following a rupture of this size is not
05:05negligible.
05:05It is statistically significant.
05:08The 5 volts is running full aftershock sequence monitoring,
05:11recalculating fault stress models in real time,
05:13and assessing which adjacent segments moved closer to their own threshold
05:17because of what happened this morning.
05:18Davao City, a metropolitan area of approximately 1.8 million people,
05:23reported shaking equivalent to a magnitude 6.7 at 7.38 in the morning,
05:28one minute after the main shock.
05:30Nearly 2 million people at breakfast time on a Monday.
05:32The timing and the secondary magnitude tell us something important.
05:36The rupture propagated directionally, radiating its most intense energy toward the city.
05:40That pattern is consistent with a fault rupture moving northwest from the hypocenter,
05:45which aligns with the orientation of the fault segment that geophysicists had flagged as a seismic gap.
05:50The last major event in this region was the Moro Gulf earthquake of 1976.
05:55Moment magnitude 7.9.
05:58It generated a tsunami that struck the coastlines of Mindanao and Sulu
06:01and became one of the most devastating natural events in Philippine history.
06:05Entire coastal communities were swept away.
06:07That event shaped Philippine disaster policy for a generation.
06:10Today's earthquake released roughly four times the energy of the 1976 rupture.
06:15The moment magnitude scale is logarithmic.
06:17Each whole number increase represents approximately 32 times more energy.
06:21From 7.9 to 8.2 is not a small step.
06:25It is a geological leap.
06:26The tsunami generated by this morning's event will behave the way shallow rupture tsunamis always behave.
06:32Invisible in the open ocean, traveling at 800 to 900 kilometers per hour, 500 to 560 miles per hour,
06:39and compressing dramatically as it enters shallow coastal waters.
06:42A wave that measures half a meter, 1.6 feet, in the open Pacific, can arrive at a shoreline as
06:48a wall of water 3 to 5 meters, 9.8 to 16.4 feet, high.
06:53The geography of Mindanao's southern coastline, particularly the shallow bays and inlets around General Santos City and Sarangani Province,
07:00creates exactly the conditions where tsunamis compress and amplify most violently.
07:05Here is what the science tells us beyond the immediate emergency.
07:09Every time a major fault ruptures, it changes the stress state of the surrounding crust.
07:13The Philippine fault does not exist in isolation.
07:15It connects to a web of structures.
07:17The Kotobato fault, the Makilala Malungan fault, the segments of the trench systems flanking the archipelago.
07:23Each of those structures has its own loading history, its own interseismic cycle, its own position on the spectrum between
07:29early loading and imminent failure.
07:31When seismologists map Coulomb's stress changes following this morning's rupture,
07:35they will identify which of those structures received additional stress,
07:38and that map will update every fault hazard assessment in the southern Philippines.
07:42This is not speculative. This is how plate tectonics works.
07:46The earth moves, the plates move, the stress builds, the faults fail, and when one fails,
07:51it changes the odds for every connected structure around it.
07:54So, here's the question I need you to answer in the comments, because I read every single one.
07:59If seismologists had already identified this fault segment as a seismic gap,
08:03a locked, charged zone, years before this morning,
08:06what does that tell you about every other locked segment that has already been mapped and flagged on active fault
08:11systems around the world?
08:12Because there are dozens of them, and the science is unambiguous about what locked faults eventually do.
08:18Not if, when.
08:19If you want to understand how the Ring of Fire connects Mindanao's fault system to the subduction zones beneath South
08:25America,
08:26Japan, and the Pacific Northwest,
08:28and what today's rupture changes about the risk picture for all of them,
08:31the next video is right there.
08:33The research on this will surprise you.
08:34I'll see you in it.
08:35I know from across the lines,
08:35you will certainly see it.
08:35Which is над As an atheist.
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