Saturday, April 16, 2016

Phivolcs not reporting some strong earthquakes?

In this period of our earthly existence which Internet chatter has often called the 'end times' period in view of of incredible weather anomalies occurring one after another, significant increase in strong earthquakes daily and getting stronger, volcanic eruptions that include the awakening of volcanoes (around forty erupting now), that have not shown activity for hundreds of years, animals and birds dying by the thousands, bees by the millions in various parts of the world, countless sinkholes popping up just about everywhere, the occurrence of something unheard of - a different type of thunderbolts that emanate not from the atmosphere but from the surface of the earth, the magnetic poles shifting at an unimaginable speed, increasing number of fireballs falling from the sky many of which have never been tracked before, and so many other freak phenomenon that they could be labelled 'apocalyptic manifestations', indeed, so we have to pay attention.

A rescue worker carries an eight-month-old baby girl after she was pulled
from the rubble following the earthquake in Mashiki, Kumamoto Prefecture. CNN photo

Again, we have to pay attention. You still have loved ones don't you?

Just last night, a very large M7.1 earthquake hit southwestern Japan in the same location where residents are still reeling from the damage, deaths and injury an earlier earthquake had caused, and just as residents were still trooping to safer grounds. This was the seventh strong earthquake of M6+ I have monitored that has hit our planet in less than 72 hours. Normal?

Living in the Philippines which sits on the Pacific Ring of Fire, we're familiar with earthquakes, at times even feeling the swarm of earthquakes for many days (such as the swarm of earthquakes in Marinduque that preceded the 2013 Bohol earthquake which killed thousands, the actual number still being debated).

What's going on here?

It is natural therefore for one to check what's going on in the Philippines as far as tectonic and volcanic events are concerned. To my surprise, international earthquake monitoring agencies (USGS, EMSC, Earthquake-Report among them) are reporting a "strong" Philippine earthquake (M5.1), that occurred on April 15, 2016, 197 km SE of Sarangani. So I checked the Phivolcs website which should normally be the first to report it. Nada!

To think that on April 5, 2016 Phivolcs reported on a M5.9 that occurred "413 km S 49 degrees E of Sarangani (Davao Occidental), therefore farther, was properly reported by Phivolcs.

Random checking showed that per USGS another strong earthquake that occurred on April 6, 2016 at 22:19:20 with M5 near Sarangani at Depth of 10 km, had the same fate as this April 15  "M5.1 197 SE of Sarangani". Both were not reported by Phivolcs on their site. For now, there seems to be no point in checking if there are other such unreported events, but... 

But Phivolcs should be reminded.

M5.9 earthquake on April 5, 2016
413 km East of Sarangani was reported by Phivolcs

M5 (M5.1) earthquake on April 6, 2015 with Depth of 10 km at 22:19:20

Above list from Phivolcs does not register the April 6, 2016 M5 earthquake at Depth of 10 km near Sarangani 

Just to think that the Celebes Sea where these tremors are happening quite often now, part of that Sea is the Moro Gulf, site of the little known 1976 earthquake-caused tsunami that killed 5,000 to 8,000 Filipinos (mainstream media did not cover that one, honest), and a very large M7.4 in July 2010, raises very serious concerns! 

What if these swarm of strong earthquakes turn out to be the silent precursors for a mega one out to change the course of our lives as we know it?

April 14, 2016 Zamboanga earthquake.
This one was reported by all relevant scientific agencies.

We have to consider that the Philippine Sea plate is at the heart of these recent large earthquakes, probably the reason why USGS has just updated yesterday, April 15, 2016, its scientific data on  Seismotectonics of the Philippine Sea and Vicinity (reproduced below). 

This USGS update came with the Sarangani tremor that Phivolcs failed to report.

In part it says: The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate.

Yesterday's (April 15) M5.1 - 197 km SE of Sarangani
recorded by USGS is NOT on Phivolcs' site

Phivolcs list of earthquakes April 15-April 16, 2016, as of publishing time
Another USGS update showing the same M5.1 tremor and Japan quakes same day
M5.1 - 197km SE of Sarangani, Philippines
Contributed by US1 last updated 2016-04-15 11:33:49 (UTC)
Time


  1. 2016-04-15 11:05:32 (UTC)
  2. 2016-04-15 19:05:32 (UTC+08:00) in your timezone
  3. Nearby Places
  • 197.0 km (122.4 mi) SE of Sarangani, PH
  • 231.0 km (143.5 mi) SSE of Caburan, PH
  • 251.0 km (156.0 mi) SE of Glan, Philippines
  • 257.0 km (159.7 mi) SE of Malapatan, PH
  • 933.0 km (579.7 mi) WSW of Koror Town, Palau

Seismotectonics of the Philippine Sea and Vicinity


The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).

South of the Mariana arc, the Pacific plate is subducted beneath the Yap Islands along the Yap trench. The long zone of Pacific plate subduction at the eastern margin of the Philippine Sea Plate is responsible for the generation of the deep Izu-Bonin, Mariana, and Yap trenches as well as parallel chains of islands and volcanoes, typical of circum-pacific island arcs. Similarly, the northwestern margin of the Philippine Sea plate is subducting beneath the Eurasia plate along a convergent zone, extending from southern Honshu to the northeastern coast of Taiwan, manifested by the Ryukyu Islands and the Nansei-Shoto (Ryukyu) trench. The Ryukyu Subduction Zone is associated with a similar zone of back-arc extension, the Okinawa Trough. At Taiwan, the plate boundary is characterized by a zone of arc-continent collision, whereby the northern end of the Luzon island arc is colliding with the buoyant crust of the Eurasia continental margin offshore China.

Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. The tectonic setting of the Philippines is unusual in several respects: it is characterized by opposite-facing subduction systems on its east and west sides; the archipelago is cut by a major transform fault, the Philippine Fault; and the arc complex itself is marked by active volcanism, faulting, and high seismic activity. Subduction of the Philippine Sea Plate occurs at the eastern margin of the archipelago along the Philippine Trench and its northern extension, the East Luzon Trough. 

The East Luzon Trough is thought to be an unusual example of a subduction zone in the process of formation, as the Philippine Trench system gradually extends northward (Hamburger et al., 1983). On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller less well-developed Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south (Cardwell et al., 1980). At its northern and southern terminations, subduction at the Manila Trench is interrupted by arc-continent collision, between the northern Philippine arc and the Eurasian continental margin at Taiwan and between the Sulu-Borneo Block and Luzon at the island of Mindoro. 

The Philippine fault, which extends over 1,200 km within the Philippine arc, is seismically active. The fault has been associated with major historical earthquakes, including the destructive M7.6 Luzon earthquake of 1990 (Yoshida and Abe, 1992). A number of other active intra-arc fault systems are associated with high seismic activity, including the Cotabato Fault and the Verde Passage-Sibuyan Sea Fault (Galgana et al., 2007).

Relative plate motion vectors near the Philippines (about 80 mm/yr) is oblique to the plate boundary along the two plate margins of central Luzon, where it is partitioned into orthogonal plate convergence along the trenches and nearly pure translational motion along the Philippine Fault (Barrier et al., 1991). Profiles B and C reveal evidence of opposing inclined seismic zones at intermediate depths (roughly 70-300 km) and complex tectonics at the surface along the Philippine Fault.

Several relevant tectonic elements, plate boundaries and active volcanoes, provide a context for the seismicity presented on the main map. The plate boundaries are most accurate along the axis of the trenches and more diffuse or speculative in the South China Sea and Lesser Sunda Islands. The active volcanic arcs (Siebert and Simkin, 2002) follow the Izu, Volcano, Mariana, and Ryukyu island chains and the main Philippine islands parallel to the Manila, Negros, Cotabato, and Philippine trenches.

Seismic activity along the boundaries of the Philippine Sea Plate (Allen et al., 2009) has produced 7 great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui and the 1995 Kobe (Japan) earthquakes (99,000, 5,100, and 6,400 casualties, respectively), the 1935 and the 1999 Chi-Chi (Taiwan) earthquakes (3,300 and 2,500 casualties, respectively), and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon (Philippines) earthquakes (7,100 and 2,400 casualties, respectively). There have also been a number of tsunami-generating events in the region, including the Moro Gulf earthquake, whose tsunami resulted in more than 5000 deaths.

The Philippine Sea Plate

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Susong Dalaga Hill from Bagtasan isthmus

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