Download Spring and Well Monitoring WARNING SYSTEM

Spring and Well Monitoring
Alert Level Scheme for Mayon Volcano
Water levels of reference wells and springs are
also being measured as possible monitor of ground
deformation. They may also give some indication on
the possible effects of volcanic activity on ground
water such as change in temperature and rate of
flow. Springs and wells around Mayon Volcano are
measured regularly for flow rate, temperature and
pH.
Alert
Level
0
No Alert
WARNING SYSTEM
A volcano Alert Level Scheme was designed for
use in information dissemination regarding the
condition
of
Mayon
Volcano. The alert status
is included in volcano
updates or bulletins issued
to inform the disaster
management agencies and
the public. Danger zones
were also
delineated,
which served as basis for
evacuation.
The area
within 6-km radius from
the summit of the volcano
is regarded as Permanent
Danger
Zone
(PDZ),
where danger is present at
all times and the hazard
involved during eruption is
high.
Once eruption
becomes imminent, the
PDZ is declared off limits.
With
the
current
morphology of Mayon, the
danger zone can be
extended to 8 to 10 km
particularly
in
the
southeast sector as the
activity intensifies.
Mayon Volcano
Network (2004)
Monitoring
Spring measurement at Bañadero, Daraga
1
Abnormal
2
Increasing
Unrest
3
Increased
Tendency
Towards
Eruption
4
Hazardous
Eruption
Imminent
5
Hazardous
Eruption
Main Criteria
Quiet.
All monitored parameters within
background levels.
Low level unrest.
Slight increase in seismicity.
Slight increase in SO2 gas output
above the background level.
Very faint glow of the crater may
occur but no conclusive evidence
of magma ascent.
Phreatic explosion or ash puffs
may occur.
Moderate unrest.
Low to moderate level of seismic
activity. Episodes of harmonic
tremor.
Increasing SO2 flux.
Faint / intermittent crater glow.
Swelling of edifice may be
detected.
Confirmed reports of decrease in
flow of wells and springs during
rainy season.
Relatively high unrest.
Volcanic quakes and tremor may
become more frequent.
Further increase in SO2 flux.
Occurrence of rockfalls in summit
area.
Vigorous steaming / sustained
crater glow.
Persistent swelling of edifice.
Intense unrest.
Persistent tremor, many “low
frequency”-type earthquakes.
SO2 emission level may show
sustained increase or abrupt
decrease.
Intense crater glow. Incandescent
lava fragments in the summit area.
Hazardous eruption ongoing.
Occurrence of pyroclastic flows,
tall eruption columns and
extensive ashfall.
Interpretation/
Recommendations
No eruption in foreseeable
future.
Entry in the 6-km radius
Permanent Danger Zone (PDZ)
is not advised because phreatic
explosions and ash puffs may
occur without precursors.
No eruption imminent.
Activity may be hydrothermal,
magmatic or tectonic in origin.
No entry in the 6-km radius
PDZ.
Unrest probably of magmatic
origin; could eventually lead to
eruption.
6-km radius Danger Zone may
be extended to 7 km in the
sector where the crater rim is
low.
Magma is close to the crater.
If trend is one of increasing
unrest, eruption is possible
within weeks.
Extension of Danger Zone in the
sector where the crater rim is
low will be considered.
Hazardous eruption is possible
within days.
Extension of Danger zone to 8
km or more in the sector where
the crater rim is low will be
recommended.
Pyroclastic flows may sweep
down along gullies and
channels, especially along those
fronting the low part(s) of the
crater rim.
Additional danger areas may be
identified as eruption progresses.
Danger to aircraft, by way of ash
cloud encounter, depending on
height of eruption column and/or
wind drift.
BACKGROUNDER
Mayon Volcano in Albay Province, known for
its almost perfect cone, is one of the 8 active
volcanoes out of the 22 active volcanoes in the
Philippines that the Philippine Institute of
Volcanology and Seismology (PHIVOLCS) is
closely monitoring.
The first seismograph at Mayon was installed in
1953 at the Bureau of Air Transportation building in
Legazpi City. In early 1960's, the Sta. Misericordia
Observatory (SMO) was established 9.8 km east of
the crater. In 1968, the Mayon Resthouse
Observatory
(MRHO)
was
constructed
approximately 4 km NNW of the summit at an
elevation of 760 m above sea level.
Each
observatory was equipped with seismographs,
watertube tiltmeters, raingauge and telescopes and
manned by volcanologists and observers who
conducted
visual
observations,
analyzed
seismograms and tiltmeter data. When the Lignon
Hill Observatory (LHO) was constructed in 1989, it
became the main observatory in Mayon and the
receiving station of telemetered seismic network.
All of the monitoring activities in Mayon are now
centered at LHO, which is situated along the flank of
Lignon Hill, a cindercone at the SE slope of Mayon.
At present, SMO is no longer manned while MRHO
serves as seismic and tiltmeter station.
monitoring methods for detecting a growing
volcanic unrest.
At Mayon, the seismic network consists of
analog and digital telemetry. The old analog seismic
network consisted of five telemetered seismic
stations. At present, only the Upper Anoling station
is operational alongside with the digital seismic
network established by the PHIVOLCS-Japan
International Cooperation Agency (JICA) Project
Phase II. Phase IIA established the mobile stations at
Upper Masarawag, Upper Mayon Rest House
(MRH) and Lignon Hill Observatory with repeater
stations at Ligao and Camalig. Phase IIB, on the
other hand, constructed permanent stations at Upper
Anoling, Upper Sta. Misericordia, MRH and LHO
with repeater sites at Mt. Bariw, Upper Sto.
Domingo and Tabaco.
Seismic Observations
Seismic method deals with the study of various
types of volcanic earthquakes and tremor detected at
Mayon Volcano and their meaning with regard to the
volcano’s activity. It is among the most reliable
COSPEC or correlation spectrometer is used for
measuring sulfur dioxide flux of a volcano. A high
SO2 emission rate is a clear indication of magmatic
activity. Sulfur dioxide emission rate at Mayon is
measured by mounting the COSPEC at the back of a
vehicle for land traverse underneath the volcanic
plume. This is usually done along the roads at
Camalig, Guinobatan, Ligao and Tabaco depending
on the direction of the plume. However, if the width
of the plume is small, the instrument is mounted on a
tripod at LHO.
of Mayon runs from Buang Junction to MRH in
Tabaco, totaling to 20 benchmarks. Another line at
the SE slope runs at Lidong with 13 benchmarks..
Continuous GPS surveys are conducted with nine
stations located around Mayon Volcano. These
stations are Lignon Hill in Legazpi, San Andres in
Sto. Domingo, Calbayog in Malilipot, Mayon
Resthouse in Tabaco, Malinao, Nabonton in Ligao,
Upper Anoling, Tinago, and Palanog in Camalig.
GPS receiver
at Calbayog,
Malilipot
Electronic tilt station
at Lower Anoling
Tripod-mounted COSPEC at LHO
MONITORING METHODS
Several methods are used to monitor Mayon
Volcano’s activities. These are: a) seismic b) gas
chemistry (COSPEC), c) geodetic (ground
deformation), d) visual and near-infra red
observations.
Gas Chemistry
Seismic instrument set-up at Lignon Hill Observatory
Ash puff
seismic
signatures on
26 July 2001
at 7:45 am,
recorded at
LHO
Ground Deformation
Visual Observations
Geodetic methods measure the amount of
ground deformation (inflation or tilting) at the
volcano’s slopes using precise leveling instrument
tiltmeter and Global Positioning System (GPS).
On the other hand, visual observations at the
summit and slopes of the volcano are conducted to
observe changes in steam emission, presence of
crater glow, ground fissuring, landslides or rock
fallsc. The upper floor of LHO has an excellent
view deck as the wall facing the volcano is covered
with glass facilitating ocular observation. The
observatory is also equipped with visible and nearinfra red cameras taking real-time pictures which are
sent to the web.
Fixed electronic tiltmeters are located at MRH,
Buang and Upper Anoling. The JICA Phase IIA
Project also installed mobile electronic tilt stations at
Upper and Lower Anoling and at Upper MRH. On
the other hand, precise leveling line at the NW slope