April 15, 2016 - CALIFORNIA, UNITED STATES - The crater measures about 75 feet by 45 feet. Regardless, class remained
in session Tuesday at Linda Esperanza Marquez High School in Huntington
Park, California.
The school, which opened in 2013, is built on the rubble of "a former toxic concrete mountain" known as "La Montaña."
But according to officials, there is no known correlation between the current crater and the ground beneath the school.
Sinkhole or man-made?
News channels describe the collapse in the concrete as a sinkhole. In
contrast school officials argue the crater is the result of an
underground water retention and recharge system built during the
school's construction in 2012.
WATCH: Giant sinkhole swallows up basketball court.
La Montaña
"La Montaña de la muerte" - "the mountain of death" - was a five-story
high pile of concrete debris and crushed asphalt collected from freeways
damaged by the 1994 Northridge earthquake.
The 600,000 ton pile of rubble, which stood so long that trees were
growing from it caused major health problems for residents of Huntington
Park.
For the ground to collapse or a sinkhole to form you need at least two
things: a soluble or unstable soil and water. La Montaña is very labile
and the underground water retention and recharge system brings in the
needed humidity.
Both are thus probably responsible for the collapse of this basketball court in Huntington Park, LA! - Strange Sounds.
April 15, 2016 - AUSTRALIA - Lynton Brown caught this 22-degree lunar halo this week and posted it to
EarthSky Facebook.
We see many, many photos of this type of halo -
both around the sun and moon - which happen all over the world due to
the presence of ice crystals in high cirrus clouds.
April 15, 2016 - JAPAN - A magnitude-7.1 earthquake has hit Japan near the city of Kumamoto on
the island of Kyushu, the Japan Meteorological Agency reported. Tsunami
warnings have been issued.
The epicenter of the quake in southern Japan was located at a shallow
depth of 10 kilometers, near the area where a 6.5 earthquake struck on
Thursday.
According to the US Geological Survey, the quake had a magnitude of 7.0
and its epicenter was located just 1 km southwest of the city of
Kumamoto.
USGS shakemap intensity.
An aftershock of 5.8 magnitude has also been reported in the area.
"Tsunami warnings or advisories are currently in effect," Japan Meteorological Agency said.
WATCH: Japan quake death toll rises.
The tsunami advisory has been issued for the Ariake and Yatsushiro Seas.
The advisory warns of a possible wave of one meter in height, Japan's NHK broadcaster said.
USGS Tectonic Summary
The April 15, 2016 M 7.0 earthquake north of Kumamoto, on the island of
Kyushu in southwest Japan, occurred as the result of strike-slip
faulting at shallow depth. Focal mechanisms for the earthquake indicate
slip occurred on either a left-lateral fault striking to the northwest,
or on a right-lateral fault striking northeast. While the earthquake
occurred several hundred kilometers northwest of the Ryukyu Trench,
where the Philippine Sea plate begins its northwestward subduction
beneath Japan and the Eurasia plate, the shallow depth and faulting
mechanism of this earthquake indicate it occurred on a crustal fault
within the upper Eurasia plate. At the location of this event, the
Philippine Sea plate converges with Eurasia towards the northwest at a
velocity of 58 mm/yr.
The April 15, 2016, M 7.0 event (UTC 16:25:06) occurred one day after a
series of foreshocks in the same region, which included M 6.2 and M 6.0
earthquakes. The April 14 events resulted in at least 9 fatalities and
over 800 injuries.
In contrast to this recent sequence of shallow earthquakes, most
seismicity in the Kyushu region is related to the subduction of the
Philippine Sea plate at depth. Just thirteen M 5+ earthquakes have
occurred at shallow depths (< 50 km) within 100 km of the April 2016
events over the preceding century. In January and April of 1975, two
shallow events with magnitudes of M 5.8 and M 6.1 - 40 km and 65 km to
the northwest of the April 2016 earthquake, respectively – caused
injuries, but no known fatalities. A shallow M 6.6 earthquake in March
2005, just off the north coast of Kyushu and 110 km north of the April
2016 event, caused over 1000 injuries and at least one fatality.
Mapped faults in the region generally trend east-west or
northeast-southwest, in agreement with the right-lateral plane of
preliminary focal mechanisms, and the trend of early aftershocks. Since
the April 14, M 6.2 event (12:26:36 UTC), 19 other shocks have been
located, including the latest M 7.0 earthquake.
USGS 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 (Magnitude greater than 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.
USGS plate tectonics.
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
(Magnitude greater than 8.0) earthquakes and 250 large (Magnitude
greater than 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.
April 15, 2016 - NEPAL - Two people were killed and two others injured in separate lightning incidents here in the district.
According to DSP Ram Bahadur KC, district police chief, the deceased
have been identified as Bishnu Kumari Rajbhandari, 65, of Phungling
Bhintuna of the district.
She felt unconscious and consequently died after the lightning struck her when she was working in the kitchen.
Likewise, Ambika BK, 22, of Taplejung Municipality-3 succumbed to death as she suffered full burn on her body when lightning struck her on March 28.
She breathed her last while being treated at BP Koirala Health Science Academy Dharan.
Similarly, two people have been seriously injuredhere
in Phurumbu VDC of the district in a lightning incident.
The injured are
Shukrabir Bhattarai, 50 and his wife whose name is yet to be
ascertained. Both are undergoing treatment at District Hospital. - Republica.
