Structural setting of the Bicol Basin and kinematic analysis of fractures on Mayon Volcano, Philippines

Lagmay, A. M. F. A.; Tengonciang, Arlene Mae P.; Uy, Homerson

doi:10.1016/j.jvolgeores.2004.11.015

Cited by 19 publications

(12 citation statements)

References 20 publications

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“…A clear example of this geodynamic arrangement is the oblique convergence between the Philippine Sea Plate and the Philippine archipelago (Fitch, 1972), forming the left-lateral Philippine Fault System (PFS). Lagmay et al (2005) focus on the justly famous Mayon Volcano (2,463 m), located on the Bicol Peninsula in the south-eastern part of Luzon Island. Their structural analysis reveals that the growth of the volcano is most likely linked to a major releasing bend in the PFS, characterized by substantial transtensional deformation.…”

Section: Subduction Zonesmentioning

confidence: 99%

Volcanism in Reverse and Strike-Slip Fault Settings

Tibaldi

Pasquarè

Tormey³

2009

New Frontiers in Integrated Solid Earth Sciences

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Traditionally volcanism is thought to require an extensional state of stress in the crust. This review examines recent relevant data demonstrating that volcanism occurs also in compressional tectonic settings associated with reverse and strike-slip faulting. Data describing the tectonic settings, structural analysis, analogue modelling, petrology, and geochemistry, are integrated to provide a comprehensive presentation of this topic. An increasing amount of field data describes stratovolcanoes in areas of coeval reverse faulting, and shield volcanoes, stratovolcanoes, and monogenic edifices along strike-slip faults, whereas calderas are mostly associated with pull-apart structures in transcurrent regimes. Physically-scaled analogue experiments simulate the propagation of magma in these settings, and taken together with data from subvolcanic magma bodies, they provide insight into the magma paths followed from the crust to the surface. In several transcurrent tectonic plate boundary regions, volcanoes are aligned along both the strikeslip faults and along fractures normal to the local least principal stress (σ 3 ). At subduction zones, intraarc tectonics is frequently characterised by contraction or transpression. In intra-plate tectonic settings, volcanism can develop in conjunction with reverse faults or strike slip faults. In most of these cases, magma appears to reach the surface along fractures striking parallel to the local σ 1 . In some cases, there is a direct geometric control by the substrate strikeslip or reverse fault: magma is transported beneath A. Tibaldi ( ) Department of Geological Sciences and Geotechnologies, University of Milan-Bicocca, Italy e-mail: alessandro.tibaldi@unimib.it the volcano to the surface along the main faults, irrespective of the orientation of σ 3 . The petrology and geochemistry of lavas erupted in compressive stress regimes indicate longer crustal residence times, and higher degrees of lower crustal and upper crustal melts contributing to the evolving magmas when compared to lavas from extensional stress regimes. Small volumes of magma tend to rise to shallow crustal levels, and magma mixing is common in the compressional regimes. In detailed studies from the Andes and Anatolia, with geographic and temporal coverage with which to compare compressional, transcurrent and extensional episodes in the same location, there do not appear to be changes to the mantle or crustal source materials that constitute the magmas. Rather, as the stress regime becomes more compressional, the magma transport pathways become more diffuse, and the crustal residence time and crustal interaction increases.

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Section: Subduction Zonesmentioning

confidence: 99%

Volcanism in Reverse and Strike-Slip Fault Settings

Tibaldi

Pasquarè

Tormey³

2009

New Frontiers in Integrated Solid Earth Sciences

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“…In fact, Figure 6 shows that, with this secondary body, the modelled gravity displays a pattern for the stations located northward from the San Vicente-Linao Fault that is rather different from the pattern for the southern stations. Therefore, we can conclude that this two-source model suggests the existence of a significant discontinuity effect due to the San Vicente-Linao Fault (LAGMAY et al, 2005) on the deformation pattern determined by the volcanic activity in Mayon Volcano. The San Vicente-Linao Fault, SW of Mayon, appears as a northwest-trending left-handed normal-slip fault (LAGMAY et al, 2005).…”

Section: Resultsmentioning

confidence: 63%

“…Therefore, we can conclude that this two-source model suggests the existence of a significant discontinuity effect due to the San Vicente-Linao Fault (LAGMAY et al, 2005) on the deformation pattern determined by the volcanic activity in Mayon Volcano. The San Vicente-Linao Fault, SW of Mayon, appears as a northwest-trending left-handed normal-slip fault (LAGMAY et al, 2005). We have observed that when we try to obtain a one-source model, without considering a second source, the discontinuity of data can produce (as is typical in these situations) sources that are displaced and too shallow.…”

Section: Resultsmentioning

confidence: 63%

“…We conclude, however, that the point-source inversion suggests a discontinuity phenomenon whose consideration as a model of the San Vicente-Linao Fault provides an optimal fit of the Mayon data, using one very plausible source. Seismic data suggest that the San VicenteLinao Fault system is active (LAGMAY et al, 2005). The consideration of the fault influence on the interpretation of geodetic observations and their time variations may allow us to detect possible flank instability hazards.…”

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confidence: 99%

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Interpretation of 1992–1994 Gravity Changes around Mayon Volcano, Philippines, Using Point Sources

Camacho¹,

Fernández²,

Charco³

et al. 2007

Pure appl. geophys.

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Significant gravity changes observed around the Mayon Volcano (Philippines) between 1992 and 1994 at 26 stations are interpreted in terms of an increase of mass and pressure changes at several point sources modelled using a fast inversion process. This inversion approach attempts to fit gravity and elevation changes by combining a random search for the positions of the sources and a linear least-squares fit for the incremental mass, pressure and possible common regional values for gravity or elevation changes. Some stabilizer terms are included in the misfit function. Models with one and two sources were tested against the observed changes at Mayon. Models with only one-source give a best fit for a shallow source with a positive mass increment, horizontally displaced far from the summit. The study using two sources gives a best fit that is similar to the one-source model, but in addition indicates anomalous behavior at stations in the SW. Neglecting the stations located southward from a local fracture, the bestfitting model suggests one central positive mass change source, which is likely to be an intrusion of about 0.5 MU with a depth of about 5 km beneath the volcano. Standard deviation for the residuals ranges from 7-8 lGal for one-source models to 6-7 lGal for models with two sources. Both of the cases are below the error value of 9.4 lGal estimated for the gravity data, so that it is not possible to discriminate between both possible interpretations without additional information.

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“…Duquesnoy et al 1994;Tibaldi and Romero-Leon 2000;Lagmay et al 2005). Such deformation can result in flank instability (Lagmay et al 2000;Norini and Lagmay 2005), erosional loci, sedimentation, and other geologic processes that shape the volcanic edifice such as vents aligned along faults.…”

Section: Structures and Morphologymentioning

confidence: 99%

Geology and hazard implications of the Maraunot notch in the Pinatubo Caldera, Philippines

et al. 2007

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The 1991 Pinatubo eruption left 5-6 km 3 of debris on the volcano slopes, much of which has been mobilized into large lahars in the following rainy seasons. Also during the eruption, collapse, localized in part along preexisting faults, left a caldera 2.5 km in diameter that almost immediately began to accumulate a 1.6×10 8 m 3 lake. By 2001, the water had risen to the fault-controlled Maraunot Notch, the lowest, northwestern portion of the caldera rim comprising the physiographic sill of the Caldera Lake. That year, a narrow artificial canal dug into an old volcanic breccia underlying the outlet channel failed to induce a deliberate lake breakout, but discharge from heavy rains in July 2002 rapidly deepened the notch by 23 m, releasing an estimated 6.5×10 7 m 3 of lake water that bulked up into lahars with a volume well in excess of 1.6×10 8 m 3 . Lakes in other volcanoes have experienced multiple breakouts, providing practical motivation for this study. Fieldwork and high-resolution digital elevation models reveal andesites and ancient lacustrine deposits, strongly fractured and deformed along a segment of the Maraunot Fault, a prominent, steeply dipping, left-lateral fault zone that trends N35°-40°W within and parallel to the notch. Seismicity in 1991 demonstrated that the Maraunot Fault is still active. The fault zone appears to have previously been the erosional locus for a large channel, filled with avalanche or landslide deposits of an earlier eruption that were exhumed by the 2002 breakout floods. The deformed lacustrine sediments, with an uncalibrated 14 C age of 14,760±40 year BP from a single charcoal sample, attest to the existence of an earlier lake, possibly within the Tayawan Caldera, rim remnants of which survive as arcuate escarpments. That lake may well have experienced one or more ancient breakouts as well. The 2002 event greatly reduced the possibility of another such event by scouring away the erodible breccia, leaving less erodible fractured andesites and lacustrine rocks, and by enlarging the outlet channel and its discharge capacity. Several lines of evidence indicate, however, that future lahar-generating lake breakouts at the notch may keep populations of Botolan municipality downstream at risk: (1) a volume of 9.5× 10 7 m 3 of lake water remains perched 0.8 km above sea level; (2) seismicity in 1991 demonstrated that the Maraunot Fault is still active and movements of sufficient magnitude could enlarge the outlet and the discharge through it; (3) more likely, however, with or without earthquake activity, landslides from the steep to overhanging channel walls could block the channel again, and a major rainstorm could then cause a rise in lake level and sudden breakouts; (4) intrusion of a new dome into the bottom of the lake, possibly accompanied by phreatic explosions, could expel large volumes of lahar-generating water.

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Structural setting of the Bicol Basin and kinematic analysis of fractures on Mayon Volcano, Philippines

Cited by 19 publications

References 20 publications

Volcanism in Reverse and Strike-Slip Fault Settings

Volcanism in Reverse and Strike-Slip Fault Settings

Interpretation of 1992–1994 Gravity Changes around Mayon Volcano, Philippines, Using Point Sources

Geology and hazard implications of the Maraunot notch in the Pinatubo Caldera, Philippines

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