Tectonophysics 699 (2017) 244–257
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Tectonophysics
journal homepage: www.elsevier.com/locate/tecto
Tectonic geomorphology and paleoseismology of the Surigao segment of
the Philippine fault in northeastern Mindanao Island, Philippines
Jeffrey S. Perez a,⁎, Hiroyuki Tsutsumi b
a
Philippine Institute of Volcanology and Seismology - Department of Science and Technology (PHIVOLCS-DOST), PHIVOLCS Bldg., C. P. Garcia Avenue, University of the Philippines Campus,
Diliman, Quezon City 1101 Philippines
b
Department of Geophysics, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
a r t i c l e
i n f o
Article history:
Received 16 November 2016
Received in revised form 3 February 2017
Accepted 4 February 2017
Available online 6 February 2017
Keywords:
Active tectonics
Strike-slip fault
Slip rate
Recurrence interval
Historical earthquake
1879 Surigao earthquake
a b s t r a c t
The Philippine fault is a major strike-slip fault that traverses the entire Philippine archipelago for more than
1250 km and has generated at least 10 surface rupturing earthquakes for the past 200 years. To better understand
its characteristics, we have conducted review of historical earthquakes, tectonic geomorphic mapping and
paleoseismic trenching along the 100-km-long Surigao segment, the northernmost segment of the Philippine
fault on Mindanao Island. We mapped the Surigao fault based on aerial photographs and identification of welldefined geomorphic features in the field. Combining this with historical accounts and paleoseismic trenching,
we have identified and mapped the surface rupture of the 1879 Mw 7.4 Surigao earthquake. Paleoseismic
trenching conducted at two sites also led us to identify evidence of at least four surface-rupturing earthquakes
including the 1879 event during the past 1300 years.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
The Philippine fault is a sinistral strike-slip fault traversing the entire
length of the Philippine archipelago for a distance of ~ 1250 km from
northern Luzon Island southward to eastern Mindanao Island (Allen,
1962; Aurelio, 2000; Barrier et al., 1991; Rangin et al., 1999; Tsutsumi
and Perez, 2013) (Fig. 1a). This NNW-trending, arc-parallel fault is a
consequence of the oblique subduction of the northwest-moving oceanic Philippine Sea plate beneath the Philippine archipelago (Aurelio,
2000; Fitch, 1972). Based on interpretation of aerial photographs and
satellite images, field surveys and seismicity, this fault was found to be
one of the most important active tectonic structures in the western Pacific region with pronounced tectonic geomorphic features such as fault
scarps, offset streams, elongated depressions, sag ponds, and pressure
and shutter ridges (Allen, 1962; Aurelio et al., 1991; Barcelona, 1981;
Nakata et al., 1977; Pinet and Stephan, 1990; Pubellier et al., 1991,
1993; Quebral et al., 1996; Ringenbach et al., 1993; Rutland, 1968;
Tsutsumi and Perez, 2013).
The Philippine fault has been seismically active for the past two centuries with more than 10 earthquakes greater than M 7 (Bautista and
Oike, 2000) (Fig. 1a). The 1990 Ms 7.8 central Luzon earthquake was
⁎ Corresponding author.
E-mail addresses: jeffrey.perez@phivolcs.dost.gov.ph (J.S. Perez),
tsutsumh@kugi.kyoto-u.ac.jp (H. Tsutsumi).
http://dx.doi.org/10.1016/j.tecto.2017.02.001
0040-1951/© 2017 Elsevier B.V. All rights reserved.
the largest and most destructive earthquake accompanied by about
120-km-long surface rupture with 6 m maximum left-lateral displacement (Nakata et al., 1996) (Fig. 1a). Other recent surface-rupturing
earthquakes along the Philippine fault are the 1973 ML 7.0 Ragay Gulf
earthquake (Morante, 1974; Tsutsumi et al., 2015) and the 2003 Ms
6.2 Masbate earthquake (PHIVOLCS Quick Response Team, 2003) (Fig.
1a).
The high seismic potential of the Philippine fault can also be recognized from recent campaign-type GPS observations that showed very
high slip rates ranging from 20 to 30 mm/year along the different segments of the fault (Aurelio, 2000; Barrier et al., 1991; Galgana et al.,
2007). From the perspective of a long-term earthquake risk assessment,
there is a need to study the Philippine fault because the fault passes
through or is close to major population centers in the country. However,
basic information to conduct this assessment for the Philippine fault,
such as the exact locations of surface traces, slip rates and recurrence intervals of surface-rupturing earthquakes, are still poorly known. Historical records of large earthquakes in the Philippines date only back to the
end of the 16th century and instrumental seismic monitoring started
only in the latter part of the 19th century (Bautista, 1999; Bautista and
Oike, 2000; Repetti, 1946; SEASEE, 1985). Paleoseismic studies in the
Philippines started in 1992 wherein the focus of the study has been
the active fault traversing Metropolitan Manila, the capital of the Philippines, (Nelson et al., 2000) and segments of the Philippine fault in Luzon
and Masbate Island (Fig. 1a) (Daligdig, 1997, Tsutsumi et al., 2006;
Tsutsumi et al., 2015; Papiona and Kinugasa, 2008). Thus, additional
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
245
Fig. 1. The seismotectonic setting of eastern Mindanao, Philippines. (a) Map showing the tectonic structures around the Philippine archipelago, the Philippine fault and epicenters (circles)
of moderate to large magnitude earthquakes (M N 6) along the Philippine fault from 1700 to 2012 (other active faults are not shown for simplicity). The rectangle shows the location of
panel b. (b) Map showing the Philippine fault and epicenters of surface-rupturing earthquakes in eastern Mindanao Island. Circles are epicenters of historical earthquakes with surface
rupture. The rectangle shows the location of Fig. 2. The trace of the Philippine fault is from Tsutsumi and Perez (2013) while the epicenters are from SEASEE (1985) and Bautista and
Oike (2000).
paleoseismological data are essential to augment the limited historical
and instrumental data for a better assessment of seismic hazards related
to the Philippine fault.
Compared to the other segments, there were few geological studies
for the Philippine fault in Mindanao Island (Fig. 1a and b). Its surface
trace location and geometry were poorly known because the fault mostly traverses the alluvial lowland and low-lying hills under thick vegetation. Tsutsumi and Perez (2013) mapped the entire length of the
Philippine fault on land including Mindanao Island (Fig. 1a and b) on
1:50,000-scale topographic maps by interpreting stereographic pairs
of ~ 1:30,000-scale aerial photographs. Perez et al. (2015) described
the distribution of the Philippine fault in Mindanao Island and suggested
that the Philippine fault is composed of several segments that are divided by geometric discontinuities such as en echelon steps, bends, changes in strike, gaps and bifurcation in the surface trace.
In this paper, we present the result of geological, geomorphological
and paleoseismological studies on the ~100-km-long Surigao segment,
the northernmost segment of the Philippine fault in Mindanao Island
(Figs. 1b and 2).We interpreted 1:30,000-scale aerial photographs
taken in 1979 and acquired from the National Mapping Resource and Information Authority (NAMRIA) of the Philippine government. After this,
we conducted geological field investigation along the Surigao segment
and identified the surface rupture associated with the 1879 Surigao
earthquake. We also reviewed the historical seismicity of the island
based on published earthquake catalogues and historical documents
(Bautista, 1999; Bautista and Oike, 2000; PHIVOLCS, 2012; Repetti,
1946; SEASEE, 1985). We then excavated paleoseismic trenches at
two sites and identified evidence of at least two and probably four surface-rupturing earthquakes during the past 1300 years.
2. Tectonic and geologic setting
The Philippine archipelago is part of a wide convergence zone between the Sunda block (an independent part of the Eurasian plate)
and the Philippine Sea plate (Fig. 1a). East of the Philippine archipelago,
the Philippine Sea plate subducts beneath the archipelago along the
Philippine trench (4°–15°N) (Cardwell et al., 1980; Fitch, 1972;
Hamburger et al., 1983) (Fig. 1a). On the western side of the archipelago, the Sunda block is being subducted from the west along the Manila
trench (13°–22°N), the Negros-Sulu trench system (6°–10°N) and the
Cotabato trench (4°–7°N) (Cardwell et al., 1980; Hamilton, 1979).
Fitch (1972) suggested a shear partitioning model for the formation of
the Philippine fault in between these two oppositely-dipping subduction zones. In this model, the Philippine trench accommodates the
trench-normal component of motion, while the trench-parallel component is being accommodated by the Philippine fault. This model has
been verified by analogue modeling (Pinet and Cobbold, 1992) and
GPS measurements (Aurelio, 2000).
Mindanao Island is the second largest island in the Philippines and
located in the southern part of the archipelago (Fig. 1a and b). Previous
geologic studies revealed that the island can be divided mainly into two
terranes based on lithologic and stratigraphic differences (Pubellier et
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J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
Fig. 2. The Surigao segment of the Philippine fault, location of trench sites and index map of the study area. Epicenter of the 1879 Surigao earthquake is from Bautista and Oike (2000).
Locations for Fig. 3a–e are shown.
al., 1991). The western terrane is composed of a continental basement
while the eastern terrane is underlain by an arc-derived Late Cretaceous
ultramafic complex capped by Paleogene volcanic rocks and Neogene
sedimentary rocks.
The study area is located in the northeastern part of Mindanao Island
(Figs. 1b and 2) and is bounded on the west by the Malimono Ridge and
on the east by the Eastern Mindanao Ridge (Fig. 2). The Malimono Ridge
is underlain by Cretaceous-Paleogene ultramafic and metavolcanic
basement rocks intruded by Late Miocene to Early Pliocene andesitic/dioritic rocks. The same basement rocks in the Eastern Mindanao Ridge
are overlain by Oligo-Miocene volcano-sedimentary sequences
(Bureau of Mines and Geosciences, 1981). In between these two ridges
are Lake Mainit and Tubay Valley (Fig. 2), which are filled with Quaternary deposits.
3. The Philippine fault in Mindanao Island
The Philippine fault traverses the entire eastern portion of the Mindanao Island from Surigao City southward to Mati City for a distance of
~320 km (Fig. 1b) (Tsutsumi and Perez, 2013). In the northern part of
the island (Figs. 1b and 2), the fault strikes N10°–20°W while it trends
almost N-S in the southern end of the island. The fault changes its strike
as it passes through the Agusan Marsh, where it is difficult to trace the
exact location of the fault because of high sedimentation rate and
some of the fault traces are submerged under water (Fig. 1b). In
Compostela area, the Philippine fault is composed of at least three
north-trending en echelon fault strands. The fault further extends and
branches southward to Mati City (Tsutsumi and Perez, 2013) (Fig. 1b).
Perez et al. (2015) characterized the distribution of the Philippine
fault in this island. They proposed that the fault is composed of several
segments that are divided by geometric discontinuities such as en echelon steps, bends, changes in strike, gaps and bifurcation in the surface
trace. Quebral et al. (1996) also showed that Philippine fault in Mindanao is restricted to a well-defined narrow zone and suggested that the
fault reactivates pre-existing collisional structures during the late Pliocene. Moore and Silver (1983) and Bischke et al. (1990) revealed the
continuation of the Philippine fault offshore south of Mindanao Island
based mainly on seismic profiles and bathymetric, gravimetric and aeromagnetic data.
Historical documents recorded possible surface-rupturing earthquakes along the Philippine fault in eastern Mindanao such as the
1879 Ms 6.9 Surigao earthquake, 1891 Ms 7.2 Davao earthquake and
1893 Ms 7.3 Monkayo earthquake (Bautista and Oike, 2000; Repetti,
1946; SEASEE, 1985) (Fig. 1b). Campaign-type GPS surveys indicate a
southward decrease in slip rate along the Philippine fault from 24 mm/year in Surigao to about 10 mm/year in Davao (Aurelio, 2000). Ohkura
et al. (2015) also suggested a slip rate of ~23 mm/year on the northern
part of Mindanao Island.
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
4. The 1879 Surigao earthquake and its surface fault rupture
Prior to instrumental seismic monitoring, the earthquake records of
the Philippines were based on historical documents such as church
chronicles and government documents written by Spanish priests and
government officials assigned in the country (Bautista and Oike, 2000;
Repetti, 1946; SEASEE, 1985). The 01 July 1879 Surigao earthquake
was the largest recorded earthquake in northeastern Mindanao (Figs.
1a, b, 2 and 3) and the only possible surface-rupturing earthquake recorded in the study area.
The 01 July 1879 Surigao earthquake was felt at 2:55 am in the entire
northeastern Mindanao and was followed by strong aftershocks for several days (Repetti, 1946; SEASEE, 1985). Most of the concrete buildings
in Surigao City, Anao-aon (now Municipality of San Francisco, a small
town west of Surigao City) and Butuan City (Fig. 2) were severely damaged due to strong ground shaking and poor construction (Repetti,
1946). Widespread liquefaction and lateral spreading were documented, as manifested by tilted and damaged buildings and bridges, fissures
247
and subsidence at Surigao City port and sand boils (Bautista, 1999;
Repetti, 1946; SEASEE, 1985). Numerous landslides were also reported
along the slopes of Eastern Mindanao Ridge and Malimono Ridge (Fig.
2) (Bautista, 1999; Repetti, 1946; SEASEE, 1985).
One of the important accounts for this earthquake was reported by
Jose Centeno, a Spanish geologist who was commissioned by the Governor General of the Philippines (Spanish Head in the Philippines) to investigate the effects of the earthquake (Repetti, 1946). The following
is an excerpt from his report:
“About 12 minutes walk south of the town there is an open plain about
1500-m-long and 500-m-wide. It is very level and on it are some houses
surrounded with betel and coconut palms. This plain suffered a drop of
about 50 cm over its whole area without noteworthy damage to the houses
and trees. The surface of the break or slip can still be seen in the slopes of the
valley and at one place a new spring of portable water has appeared…”
(Repetti, 1946).
Repetti (1946) interpreted that Jose Centeno described the surface
rupture of the 1879 Surigao earthquake as manifested by a 50-cm-
Fig. 3. Modified Mercalli Intensity (MMI) scale isoseismal and epicenter (black circle) of the 1879 Surigao earthquake. Solid black lines (with dashed line in Lake Mainit) is the trace of the
Surigao segment and the surface rupture of the 1879 Surigao earthquake while thin gray line are the trace of other segments of the Philippine fault (e.g. Esperanza segment). The isoseismal
map is from Bautista (1999).
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J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
high scarp and appearance of a spring along the tectonic scarp south of a
particular town. From the historical accounts, we identified the town of
Anao-aon (now San Francisco) as the town mentioned by Jose Centeno
and the open plain south of this town is the alluvial plain of the Anaoaon River (Figs. 2 and 4a). Allen (1962) also identified tectonic scarps
on aerial photographs between Anao-aon and Lake Mainit that is related
Fig. 4. Detailed fault map of the study area. The base map is from 1:50,000 topographic maps published by NAMRIA. Contour interval is 100 m. (a) Anao-aon to Gacepan. (b) Gacepan to
Mayag. (c) Tubay Valley. (d) Minusang Creek to Taguibo River. (e) Southern end.
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
249
Fig. 4 (continued).
to the surface fault rupture of the 1879 Surigao earthquake. Aerial photograph interpretation, field survey and paleoseismic trenching conducted in this study also revealed that the tectonic scarps along the
Tubay Valley south of Lake Mainit (Figs. 2, 4c and 6c) were also associated with the surface fault rupture of the 1879 Surigao earthquake.
Bautista (1999) have studied historical earthquakes in the Philippines from 1589 to 1895 using historical accounts and descriptions.
Based on the extent of damaged area and assessed seismic intensities
for each reported location, they have estimated the location of epicenter, the magnitude and proposed isoseismal maps for each historical
earthquake. For the 1879 Surigao earthquake, Bautista (1999) proposed
an isoseismal map with maximum Modified Mecalli Intensity (MMI) X
(Fig. 3), estimated a magnitude of 6.9 and its epicenter is located
south of Lake Mainit. They proposed that the source of this earthquake
was the Surigao segment of the Philippine fault (Figs. 1b, 2 and 3).
5.1. Anao-aon to Gacepan
Southward from Leyte Island, the Philippine fault traverses the Mindanao Sea and enters the eastern side of Mindanao Island near the town
of Anao-aon, west of Surigao City (Figs. 1, 2 and 4a). Between Anao-aon
and Lake Mainit, the fault traverses the Malimono Ridge and the alluvial
plains of the Anao-aon River and Mayag River for a distance of about
30 km (Fig. 4a and b). Immediately south of Anao-aon, it is difficult to
identify the fault trace along the course of the Anao-aon River. Further
to the south, the fault with a general strike of N15°–20°W transects
the Malimono Ridge. This fault trace was mapped using aerial photographs and was difficult to identify in the field due to thick vegetation.
A left-laterally deflected creek (location 1, Fig. 4a) and pressure ridge
(location 2, Figs. 4a and 6a) were identified in Magtangale. Most of the
fault scarps in this area are east-facing. From Magtangale, the fault is
continuous and extends further to the south for about 4 km where another parallel trace ~3 km long is identified about 500 m to the west.
5. Tectonic geomorphology of the Surigao segment of the Philippine
fault
5.2. Gacepan to Mayag
The Surigao segment as defined by Perez et al. (2015) is the northernmost segment of the Philippine fault in Mindanao Island. It is characterized by fairly continuous tectonic scarps with offset creeks, pressure
and shutter ridges, and with a general strike of N20°W. Fig. 2 shows the
location of the study area and Fig. 4a–e show the trace of the Surigao
segment originally interpreted by Tsutsumi and Perez (2013). We will
describe the tectonic geomorphic features along the Surigao segment
from north to south based on aerial photo interpretation and field geomorphic mapping.
Along the western side of Mayag River and the eastern slope of
Malimono Ridge, we identified left stepping en echelon faults that
trend N5°–10°W for a distance of about 16 km (Fig. 4b). The most distinct fault scarps, at least 1-m-high, and sag ponds were observed in
Gacepan (location 3, Fig. 4b) and the most distinct pressure ridge is
identified in Mayag (location 4, Fig. 4b). Most of the fault scarps are
west-facing which is opposite to those observed near Magtangale (location 1, Fig. 4a). Systematic sinistral offsets of streams were also identified on aerial photographs (Figs. 4b and 5). No distinct tectonic
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J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
traverses young alluvial fans (Fig. 4c). Several offset creeks were identified and most fault scarps are west-facing that generally strike N15°–
20°W. This continuous fault scarps extend for about 15 km from Jagupit
(Fig. 4c) to Minusang Creek (Fig. 4d).
Based on the tectonic landforms and paleoseismic results (refer to
Section 6.1) in this area, these tectonic scarps and offset creeks are
interpreted to be related to the surface rupture of the 1879 Surigao
earthquake. The average height of the fault scarps (0.5–1.0 m) measured in the field is consistent with the descriptions in historical documents (Repetti, 1946).
5.4. Minusang Creek to Taguibo River
Fig. 5. Example of aerial photograph that shows active fault traces (white line) and
systematic left-lateral deflection of streams (black line).
A continuous west-facing fault scarp about 500-m-long with a general strike of N20°W cuts a young alluvial fan of Minusang Creek (location 8, Figs. 4d and 6d). The maximum height of the scarp in this area is
about 10 m, suggesting multiple surface-rupturing earthquakes including the 1879 Surigao earthquake along this segment of the Philippine
fault. The fault scarps on the alluvial fan of Cabadbaran River that
were identified on aerial photographs taken in 1979 were not observed
in the field because most of the fault traces were artificially modified
due to construction of an irrigation canal. Between Cabadbaran and
Arega Rivers, the fault trace transects young alluvial fan with systematic
sinistral offsets of river channels. Sto. Niño trench site, which will be described in Section 6.2, is located on the alluvial fan of Arega River (Fig.
4d).
North of the Sto. Niño trench site, the west-facing scarp varies in
height from 1 to 2 m (Fig. 4d). Location 9 is part of the west-facing
scarp that traverses the young fluvial terraces extending from Arega
River to Taguibo River (Figs. 4d and 6e). The general strike of the fault
in this area changes from N20°W in the north (near Minusang Creek)
to N5°–10°W in the south (near Arega River).
5.5. Southern end
geomorphic features were identified along the alluvial plain of the
downstream portion of Mayag River, probably because of the sedimentation and erosion of the river deposits. South of this area, the fault follows the western margin of Lake Mainit for about 20 km (Fig. 2).
5.3. Tubay Valley
South of Lake Mainit, we have identified an east-facing, 10-km-long,
tectonic scarp with a general strike of N20°W that transects the Tubay
Valley (Fig. 4c). This tectonic scarp was clearly identified on the aerial
photographs and in the field and cuts the alluvial lowland of the westflowing Puyo and Asiga Rivers that drain into the south-flowing Tubay
River (Fig. 4c). Immediately south of Lake Mainit, an east-facing tectonic
scarp about 1 m high was recognized near the national road going to
Jabonga for a distance of 2 km (location 5, Fig. 4c). Continuous east-facing fault scarps with systematic left-lateral deflection of creeks were
identified south of Puyo River on aerial photographs taken in 1979.
However, these geomorphic features were not observed in the field because the area is now submerged underwater (Fig. 4c).
In Santiago, a west-flowing stream channel is displaced left laterally
at 5.7 ± 1 m for the northern bank and 5.3 ± 1 m for the southern bank
(location 6, Figs. 4c and 6b). This stream channel deflection can be associated with the 1879 Surigao earthquake. At location 7 (Figs. 4c and 6c),
a ~1-km-long continuous east-facing fault scarp about 50 cm high was
identified on the both sides of a dirt road. The Santiago trench site that
will be described in Section 6.1 is located ~ 300 m south of location 7
(Figs. 2 and 4c). Further to the south of the trench site, fault scarps
were not observed in the field probably because of recent sedimentation
along the Asiga River. South of the Asiga River, no fault trace can be
identified both on aerial photographs and in the field for about 4 km.
The fault trace steps to the left for about 600 m in Jagupit and appears
along the western edge of Eastern Mindanao Ridge where the fault
South of Taguibo River, the fault cuts young fluvial terraces for about
4 km before it transects the slopes of Eastern Mindanao Ridge (Fig. 4e).
The fault trace, which trends N15°–20°W, is fairly continuous and marks
the topographic boundary between the mountain ridge (Eastern Mindanao Ridge) and alluvial lowland. A shutter ridge is identified 500 m
south of Taguibo River (location 10, Fig. 4e) and systematic deflection
of creeks were also observed. The strike of the fault changes significantly
from N15°–20°W to N20°–30°W (Fig. 4e) as it enters the Eastern Mindanao Ridge. To the west of this main trace, there is a fault trace with
a 500-m-wide restraining step. Field observation in this area was limited due to thick vegetation and human modification.
The change in the strike of the fault, the presence of a restraining
step and branching of the fault to the south suggest that this is the
southern end of the Surigao segment. South of Surigao segment, we
have identified another segment of the Philippine fault, the Esperanza
segment, a 50-km-long, N15°–20°W trending segment that is characterized as a continuous east-facing scarp that is a few meters high and cuts
the alluvial plain of Agusan River (Fig. 3). In between these two segments (Surigao and Esperanza segments) is a ~ 5-km-long gap and a
restraining step of ~ 1 km. Esperanza segment passes through Agusan
Marsh area where it is difficult to delineate the trace of the fault
continuously.
6. Paleoseismic trenching along the Surigao segment
Two paleoseismic trenches (Santiago and Sto. Niño trenches) about
30 km apart were excavated across the Surigao segment to identify and
characterize its paleoseismic activity (Figs. 2, 4c, d and 7). This is the first
paleoseismic studies conducted in Mindanao Island. The 8-m-long and
3.5-m-deep Santiago trench was excavated across a less than 50-cmhigh tectonic scarp on alluvial lowland in Tubay Valley, about 10 km
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
251
Fig. 6. Photographs of typical tectonic geomorphic features of the Surigao segment. The yellow arrows indicate the location of the fault. The white arrows (Fig. 6b) show the piercing points
for lateral offsets. Refer to Fig. 4 for locations of photographs.
Fig. 7. Photographs of the two trenches excavated along the Surigao segment. (a) south wall of the Santiago trench and (b) north wall of the Sto. Niño trench. Grid interval (white line) is
1 m. Refer to Figs. 2, 4c and d for the location of the paleoseismic trenches. Detailed logs of the north and south walls of the two trenches are shown in Figs. 8 and 9.
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J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
Fig. 8. Detailed log of the north and south walls of the Santiago trench. Grid interval is 1 m. Italic numerals shown in the logs denote stratigraphic units (e.g. 40) while italic letters with
numerals indicate fault strands (e.g. FN1-6). Calibrated ages for charcoal samples are also shown (Table 1). See Fig. 4c for the location of the trench.
south of Lake Mainit (Figs. 2, 4c, 7a and 8). The Sto. Niño trench, located
on an alluvial fan of Arega River, was 10-m-long and 3.5-m-deep (Figs.
2, 4d, 7b and 9). The two single-slot paleoseismic trenches were dug
manually and we logged the north and south walls of the trenches
using vertically projected photo mosaics at a scale of 1:20 (Figs. 8 and
9). We collected charcoal and wood fragments for radiometric dating.
Selected samples were dated using a compact NEC accelerator mass
spectrometer (AMS:NES1.5SDH) at Paleo-Lab in Japan (Tables 1 and
2). In the following sections, we describe the stratigraphy and discuss
the evidence of paleoseismic events for each trench site. Fault strands
on the north and south walls are represented by FN and FS respectively.
6.1. Santiago trench site
All of the sediments, except for the two topmost layers including the
cultivated soil, were displaced by near-vertical faults, which branch upward into several strands to form a flower structure with a 3-m-wide
fault zone near the surface. The dip of the fault strands is from 60° to almost vertical. Fig. 7a is a photo of the south wall of the trench and Fig. 8
shows the detailed stratigraphic logs for the north and south walls of the
Santiago trench.
6.1.1. Stratigraphy
The strata exposed on the trench walls are alluvial fan deposits of
Asiga River (Fig. 4c). We divided the strata into six units with eight
sub-units based on lithology and stratigraphic position (Fig. 8). The six
stratigraphic units will be briefly described. Radiocarbon ages for organic samples are shown in Fig. 8 and Table 1.
Unit 60, the lowermost unit exposed on the trench walls, is composed of coarse sand to pebble in size clasts and is present only on the
upthrown side (west side) of the fault. It is overlain by Unit 50 which
is composed of fine sand and silt with charcoal fragments and is only exposed on the upthrown side of the fault. Two charcoal samples collected
from this unit (north and south walls) show ages of 660–723 AD and
665–723 AD (Fig. 8 and Table 1). Conformably overlying Unit 50 is
Unit 40, which is made up of gravels. The clasts in Unit 40 are moderately sorted and composed of pebble- to cobble-sized andesite rocks with
silty to coarse sand matrix. This unit was deposited by stream flow
with a fining upward sequence and becomes matrix supported in the
upper part. Unit 40 is also exposed only on the upthrown side of the
fault. A small pit dug 1 m below line III at S2.5–S2.8 of the south wall exposed the topmost part of Unit 40 on the downthrown side (Fig. 8).
Based on the exposed Unit 40 on the small pit, below line III at S2.5–
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
253
Fig. 9. Detailed log of the north and south walls of the Sto. Niño trench. Grid interval is 1 m. Italic numerals denote stratigraphic units while italic letters with numerals indicate fault strands.
Calibrated ages for wood and charcoal samples are also shown (Table 2). Location of trench site is shown in Fig. 4d.
S2.8, the vertical separation of the uppermost part of Unit 40 across the
fault zone was measured at 2.3 m.
Unit 30 is a flood loam deposit overlying terrace gravels of Unit 40.
Sand lenses are present within this unit (Unit 31 and 32). The thickness
of Unit 30 changes from about 50 cm on the upthrown side to about 1 m
on the downthrown side. Two charcoals collected from Unit 30 (north
wall and east wall) show ages of 892–991 AD and 986–1024 AD (Fig.
8 and Table 1). On the downthrown side of the trench walls, several
sub-units of Unit 30 were identified (Units 33–36). These sub-units
are composed of alternating layers of fine sand with silt and medium
to coarse sand. Vertical separation of the topmost part of Unit 30 across
the fault zone is about 1.1 m. Unit 20 is a paleosoil with the same
thickness (about 45 cm) across the fault zone on the south wall. On
the north wall, the thickness of Unit 20 changes east of N3.5 due to erosion. Vertical deformation of the topmost part of Unit 20 across the fault
zone on the south wall is about 0.7 m. Unconformably overlying Unit 20
is Unit 11, composed of humic soil. Within this unit is a lenticular channel deposit (Unit 12), composed of coarse sand to pebble. On top of this
is the cultivated soil layer of Unit 10.
Units 30, 36, 50 and 60 are in fault contact with Unit 40 and standing
gravels were observed along the fault zone (Fig. 8). FN1-8, FN1-9, FS1-7
and FS1-8 were identified 1 m east of the main fault zone. These fault
strands cut units below Unit 30 on the north wall and Unit 34 on the
south wall.
Table 1
Radiocarbon ages from Santiago trench.
Sample no.
Lab. no. (PLDa)
Unit
Trench grid location (horizontal/vertical)
Material
14
sant315-01
sant315-02
sant315-03
sant315-04
13,027
13,865
13,866
13,028
30
30
50
50
N1.31/II.33
east wall/II.21
N6.85/II.85
S6.31/II.73
Charcoal
Charcoal
Charcoal
Charcoal
1100
1030
1300
1305
a
b
C Age (years BP)
±
±
±
±
20
15
20
20
PLD: Paleo Labo Co., Ltd., Japan.
Calibrations were performed using OxCal Program v4.1 (Ramsey, 1995) and calibrated using IntCal09 Calibration Curves (Reimer et al., 2009).
Calibrated age (cal. years ± 2σ)b
892–991 AD
986–1024 AD
665–723 AD
660–723 AD
254
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
Table 2
Radiocarbon ages from Sto. Niño trench.
Sample no.
Lab. no. (PLDa)
Unit
Trench grid location (horizontal/vertical)
Material
14
Calibrated age (cal. years ± 2σ)b
stnin317-03
stnin317-01
13,867
13,029
60
61
east wall/II.43
N0.90/II.47
charcoal
wood
1130 ± 15
1145 ± 20
886–974 AD
856–973 AD
a
b
C Age (years BP)
PLD: Paleo Labo Co., Ltd., Japan.
Calibrations were performed using OxCal Program v4.1 (Ramsey, 1995) and calibrated using IntCal09 Calibration Curves (Reimer et al., 2009).
6.1.2. Geologic evidence for paleoseismic events and their ages
We identified geologic evidence of at least four surface-rupturing
events including the 1879 Surigao earthquake in Santiago trench (Fig.
8).
limitation of the depth of the trench we cannot confidently interpret
these seismic events.
6.1.2.1. Event A. FN1-4, FS1-3 and FS1-6 cuts all the units except for Units
10, 11 and 12. The event horizon for the latest event is the top of or during the deposition of Unit 20, as manifested by upward termination of
faults (FN1-4, FS1-3 and FS1-6) near the boundary of Unit 20 and Unit
11. Unit 20 was deformed at this event, as shown by warping of Unit
20 towards the downthrown side. Although the lowermost part of
Unit 20 was not clearly offset by the faults, we interpreted that FN1-4,
FS1-3 and FS1-6 extend upward to Unit 20 based on the presence of
cracking and the differences in sediment textures across the fault
zone. The thickness of Unit 20 is constant all over the trench walls and
we interpret that before the deposition of Unit 20, the topography was
flat and the unit was deposited with the same thickness. During the deposition of Unit 20, a surface-rupturing event occurred with vertical deformation of about 0.7 m and Unit 11 subsequently filled the
topographic low, except on the upthrown side on the north wall.
Based on historical accounts, location of this trench site and analysis of
the trench walls, we interpreted that the most recent event corresponds
to the 1879 Surigao earthquake.
The strata exposed on the trench walls are composed of alluvial fan
deposits of the Arega River (Figs. 4d, 7b and 9). Near vertical fault
strands forming a flower structure displaced all the stratigraphic units
except for the cultivated soil (Fig. 9). The dip of the fault is N80° and
splays upward into several fault strands to form a 2-m-wide fault zone
near the surface (Fig. 9). Detailed topographic map and topographic
profiles across the west-facing fault scarp near the trench revealed
that the fault scarp is about 1 m high. Fig. 7b is a photo of the north
wall of the trench and Fig. 9 shows the detailed stratigraphic log for
the north and south walls of the Sto. Niño trench.
6.1.2.2. Event B. The penultimate event is manifested by the truncated
layers below Unit 20 by FN1-3 to FN1-6 and FS1-4 to FS1-5. Event B occurred during the deposition of Unit 30, as inferred from upward terminations of FN1-3, FN1-5, FN1-6, FS1-4 and FS1-5, the difference in
thickness of Unit 30 from the upthrown to the downthrown side and
the vertical deformation of Unit 30. Vertical separation of the lowermost
part of Unit 30 is about 1.1 m, which is more than that of the uppermost
part of Unit 20 (about 0.7 m) that conformably overlies this unit. We
cannot constrain the timing of the penultimate event but the age obtained from Unit 30 suggests that at least two surface-rupturing events
(Event A and B) occurred since 990 AD.
6.1.2.3. Event C. Event C occurred during the deposition of Units 35 and
30 on the north wall and Units 35 and 34 on the south wall because
the minor fault strands, FN1-8, FN1-9, FS1-7 and FS1-8, cut layers
below Unit 30 on the north wall and Unit 34 on the south wall. The vertical displacement of these layers associated with this event is relatively
smaller compared to the vertical displacement produced by the two
most recent events (Event A and B). We also interpret that the major
fault strands (FN1-4 and FS1-4 to FS1-6) moved during this seismic
event.
6.1.2.4. Event D. A surface-rupturing event occurred after the deposition
of Unit 40 based on upward termination of FN1-2 and FS1-2, and the
amount of vertical deformation of this unit. We can loosely constrain
the timing of Event C and Event D due to limited datable materials
from the trench walls. Ages obtained from Unit 50, 660–723 AD and
665–723 AD (Fig. 6 and Table 1), indicate that four surface rupturing
events (Events A, B, C and D) occurred during the past 1300 years.
Older seismic events may have occurred after the deposition of Unit
50 as manifested by upward termination of FN1-1 and FS1-1 but due to
6.2. Sto. Niño trench
6.2.1. Stratigraphy
We divided the strata into six units with seven sub-units based on lithology and stratigraphic position (Fig. 9). We will briefly describe these
units from the lowest stratigraphic position. Fig. 9 and Table 2 show the
calendar age of wood and charcoal materials collected from Units 60
and 61.
Units 60, 61 and 62 are composed of alternating layers of fine to medium sand and silty sand. These sediments are gray to black in color and
contain wood fragments that indicate a swampy depositional environment. These units are exposed only on the upthrown side of the fault
zone or east side of the trench wall. Results of 14C dating from the
wood and charcoal materials from Units 60 and 61 provide almost the
same ages, 886–974 AD and 856–973 AD (Fig. 9 and Table 2). Units 50
and 51 are matrix-supported layers composed of coarse sand and pebble clasts. These units are the lowermost units on the downthrown
side of the fault zone.
Units 40, 41, 42 and 43 are composed of layers of sand and pebbles of
different sizes, and are present on both sides of the fault zone. The overall thickness of these units is different across the fault zone from about
60 cm on the upthrown side to 20–30 cm on the downthrown side.
The vertical separation of the uppermost part of Unit 40 is about
1.5 m. Unit 30 unconformably overlies Unit 40 and is made up of flood
loam deposits composed of medium sand with silty sand, clay and pebbles. The thickness of this layer is almost the same on both sides of the
fault zone and the vertical separation of the topmost portion of this
unit by the main fault zone is about 1.5–1.7 m. Unit 20 is also a flood
loam deposit. We have differentiated these two flood loam deposits
by differences in color, degree of compaction and presence of clay
with pebbles in Unit 30. The thickness of Unit 20 varies from 70 to
80 cm on the downthrown side to 40 cm on the upthrown side. The vertical separation of the uppermost part of Unit 20 by the fault zone is
about 1 m. On top of Unit 20 are humic soil of Units 10 and 11. Unit
11 is about 60 cm thick on the downthrown side and thins out to
20 cm on the upthrown side with a vertical separation of an approximately 1 m on its lowermost part. Unit 10 is about 20-cm-thick cultivated soil.
6.2.2. Geologic evidence for paleoseismic events and their ages
Stratigraphic evidence for two surface-rupturing events was identified in Sto. Niño trench.
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
255
6.2.2.1. Event A. The youngest faulting event displaced all the sediments,
except for the cultivated soil (Unit 10) by FN2-3, FN2-4, FS2-2 and FS2-3
(Fig. 9). The latest event occurred during the deposition of Unit 11 as
manifested by upward termination of the fault strands, the vertical deformation along the fault zone of Unit 11 and 20, which is about 1 m,
and the thicker deposit of Unit 11 on the downthrown side (about
20 cm on the upthrown side compared to about 60 cm on the
downthrown side). Although the lowermost part of Unit 11 is not clearly offset by the fault strands, the extensions of FN2-3, FN2-4, FS2-2 and
FS2-3 were identified by the presence of cracking and differences of sediment textures across these fault strands. Since we cannot constrain the
age of the latest event, we interpret that this event is related to the 1879
Surigao earthquake.
MMI X (Fig. 3). The shape and size of the isoseismal map also show a
narrow elongated area along the strike of the fault that experienced
strong ground shaking of at least MMI VII. The paleoseismic trenches indicate that the dip of the Surigao segment is almost vertical near the surface (Figs. 8 and 9). This observation is consistent with the fact that the
fault trace is remarkably straight, the direction of the vertical displacement changes from place to place, a feature commonly observed for
strike-slip faults (McCalpin, 2009; Sylvester, 1988) and that the
isoseismal of the 1879 Surigao earthquake are elongated along the
strike of the fault (Bautista, 1999) (Fig. 3).
6.2.2.2. Event B. The penultimate event cuts the stratigraphic units below
Unit 20 by FN2-1 to FN2-4 and all the fault strands in the south wall (Fig.
9). FN2-1, FN2-2 and FS2-1 terminate within the lower part of Unit 20.
The thickness of Unit 30 is the same (60–70 cm) throughout the trench
walls and indicates that prior to the penultimate event there was no
scarp. Based on these observations, we suggest that the penultimate
event occurred during the deposition of Unit 20. Vertical separation of
the uppermost portion of Unit 30 is about 1.5–1.7 m, almost twice of
the vertical separation of the topmost part of Units 20 and 11, indicating
that Unit 30 probably experienced two surface-rupturing events. These
observations are consistent with the 1.5 m offset of the stratigraphic
boundary between Units 30 and 40. We cannot identify in which
event FN2-5 that terminates within Unit 30 moved. Based on vertical
separation of the different units that FN2-5 truncated, this fault strand
moved only once during the penultimate or the most recent event, or
may not have reached the ground surface during one of the
earthquakes.
We cannot constrain the timing of the penultimate event (Event B)
because of limited datable materials from the trench walls. Ages 886–
974 AD for Unit 60 and 856–973 AD for Unit 61 indicate two surfacerupturing events during the past 1100 years. The most recent event is
correlated with the 1879 Surigao earthquake.
Studies of modern surface ruptures worldwide show that mapped
surface complexities in the fault geometry such as changes in strike,
stepovers, bifurcations and fault bends and gaps strongly control and influence the nucleation and termination of faulting process (Okubo and
Aki, 1987; Schwartz and Coppersmith, 1984; Segall and Pollard, 1980;
Wesnousky, 2006). In strike-slip faults, for example, releasing steps
may act as kinematic barriers to rupture propagation (Sibson, 1985)
and often terminate along major steps, bends and in branches
(Knuepfer, 1989). The southern termination of the Surigao segment is
marked by the noticeable change in the general strike of the fault
from N15°–20°W to N20°–30°W (Figs. 3 and 4e), fault branching and
the presence of another fault located west of the end of the main
trace. There is a 500-m-wide restraining step and a gap between Surigao
and Esperanza segments (Fig. 3). Based on these observations, the total
length of the Surigao segment is estimated to be about 100 km.
Based on our review of historical accounts and the proposed
isoseismal map (Bautista, 1999), the tectonic geomorphic features observed along the surface trace of the Surigao segment, fault branching
in its southern termination, the wide gap between the Esperanza segment and the paleoseismic trenching results, we suggest that the entire
length of the 100-km-long Surigao segment probably ruptured during
the 1879 earthquake. The observed tectonic scarps (about 50 cm high)
and systematic left lateral deflection of streams (about 5 m) (Figs. 4 to
6) are also related to the latest event.
Bautista and Oike (2000) analyzed the seismic intensity of this
earthquake based on historical documents and proposed a Ms 6.9 with
the epicenter located south of Lake Mainit along the Surigao segment
(Figs. 2 and 3). If we assume that the 1879 Surigao earthquake ruptured
the entire length of the ~ 100-km-long Surigao segment (Fig. 3), the
1879 Surigao earthquake may have been at least M 7.4 based on empirical relations by Wells and Coppersmith (1994), which is significantly
larger than the estimated magnitude by Bautista and Oike (2000).
7. Discussion
7.1. Fault geometry and sense of faulting of the Surigao segment
The Philippine fault in Mindanao Island is composed of distinct fault
traces separated by geometric discontinuities, such as dilatational steps
and branching (Fig. 1b) (Tsutsumi and Perez, 2013). Its northernmost
segment, the Surigao segment, is the longest (~100-km-long) and has
generated a historical surface-rupturing earthquake, the 1879 Surigao
earthquake. The surface trace of the Surigao segment is remarkably
straight with left steps, and a general strike of N10°–20°W (Figs. 2 to 4).
Systematic left-lateral deflections of streams suggest predominant
left-lateral slip of the Surigao segment (Figs. 4 and 5). The direction of
vertical component of displacement (east side up versus west side up)
varies from place to place and is much smaller than the horizontal component of displacement, a commonly observed characteristics of surface
ruptures along strike-slip faults (McCalpin, 2009). Transtensional deformation features such as linear troughs and sag ponds are observed along
the fault zone. The high tectonic scarp (about 10 m high) mapped along
the alluvial fan of Minusang Creek (Location 8, Figs. 4d and 6d) is one of
the evidence for repeated late Quaternary faulting along the Surigao
segment. On the northern part of the segment (Fig. 4b), the fault trace
contains a series of en echelon left steps (the width of these steps are
more than 100 m). The most notable step (~600 m) is located in Jagupit
(Fig. 4c). On the southern part of the segment, the fault is fairly continuous and marks the boundary between the western margin of the Eastern Mindanao Ridge and alluvial lowland (Fig. 4d to e).
Based on the proposed isoseismal map of the 1879 Surigao earthquake (Bautista, 1999), the maximum intensity of this earthquake was
7.2. Extent of the surface rupture and the magnitude of the 1879 Surigao
earthquake
7.3. Recurrence interval and slip rate of the Surigao segment in comparison
to other segments of the Philippine fault
Recurrence interval of surface-rupturing earthquakes along the
Surigao segment was obtained from the two trench sites excavated in
this study. From the available datable materials in Santiago trench, we
identified at least four surface-rupturing events for the past
1300 years including the 1879 earthquake and at least two surface-rupturing events occurred since 990 AD (Fig. 8 and Table 1). We identified
at least two surface-rupturing events including the 1879 earthquake for
the past 1000 years in Sto. Niño trench (Fig. 9 and Table 2). Combining
the results from these two trench sites, we suggest that the recurrence
interval for the Surigao segment is about 300–1000 years. From this recurrence interval and if we assume that the coseismic displacement of
the 1879 earthquake is at least 5 m, as measured in the field, the slip
rate of the Surigao segment is calculated at 5–17 mm/year. This slip
rate is based on characteristic earthquake model (Schwartz and
Coppersmith, 1984) and is assumed that an individual fault segment
tends to generate earthquakes with the same magnitude or within
256
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
narrow range of magnitudes near the maximum. This slip rate is comparable to the previous campaign-type GPS measurements that indicate a
southward decrease in slip rate along the Philippine fault in Mindanao
Island from 24 mm/year in Surigao to 10 mm/year in Davao (Aurelio,
2000).
The relatively high slip rate and short recurrence interval of the
Surigao segment indicate a very high seismic potential, comparable to
the other segments of the Philippine fault. In central Luzon (Fig. 1a),
paleoseismic investigation showed a 500–600 years recurrence interval
for the Digdig segment that last ruptured during the 1990 Mw 7.7 Luzon
earthquake, and a slightly longer recurrence interval for the San Jose
segment (Tsutsumi et al., 2006). Along the Guinayangan segment that
ruptured in 1973, Tsutsumi et al. (2015) suggested a recurrence interval
of 360–780 years. In Masbate Island (Fig. 1a), paleoseismic studies revealed at least four surface-rupturing earthquakes during the past
680 years, including the 2003 Ms 6.2 Masbate earthquake (Papiona
and Kinugasa, 2008). South of the Surigao segment (Fig. 1b), a
paleoseismic trenching across a tectonic scarp that is related to the surface rupture of the 1893 Ms 7.3 Monkayo earthquake revealed stratigraphic evidence for multiple faulting events for the past 1700 years
(Perez and Tsutsumi, 2011).
The Surigao segment and the other segment of the Philippine fault is
also comparable to other major strike-slip faults of the world such as the
San Andreas fault (Sieh, 1978a, 1978b; Sieh and Jahns, 1984; Sieh and
Williams, 1990), the Median Tectonic Line (Tsutsumi and Okada,
1996), the North Anatolian fault (Jolivet and Faccenna, 2000;
McClusky et al., 2000), and the Sumatran fault (Sieh and Natawidjaja,
2000) which have high slip rates and relatively shorter recurrence intervals that caused large surface-rupturing earthquakes in the past.
8. Conclusions
To better understand the earthquake potential of the Philippine fault
in eastern Mindanao Island, we conducted a review of historical earthquakes, tectonic geomorphic mapping and paleoseismic investigation
along the 100-km-long Surigao segment, which is the northernmost
segment of Philippine fault on this island. We mapped well-defined tectonic geomorphic features, identified the surface rupture of the 1879
Surigao earthquake and propose a magnitude M 7.4 for this historical
surface-rupturing event that is much larger than the previous estimate.
From the two paleoseismic trenches, we identified at least four surfacerupturing events for the past 1300 years that include the 1879 Surigao
earthquake. If we assume that the coseismic lateral displacement of
the 1879 Surigao earthquake is at least 5 m, the slip rate along this segment is calculated to be 5–17 mm/year, which is comparable with the
GPS measured slip rate and with recurrence interval of about 300–
1000 years.
Results of our studies have important implications for assessing
earthquake generation potential not only for the Surigao segment, but
also for the other segments of the Philippine fault in Mindanao Island.
Our tectonic geomorphic mapping provides basic information about
the characteristics of the Philippine fault in this area while our
paleoseismic investigation augments the limited historical data. From
this, we revealed the long-term behavior of the Philippine fault and provided basic information for seismic hazard mitigation. To further identify and assess the seismic hazard of Philippine fault in the Mindanao
Island, additional paleoseismic studies should be conducted on the
other segments in the future.
Acknowledgements
This study was funded by a grant to Hiroyuki Tsutsumi from the
Ministry of Education, Culture, Sports, Science and Technology of Japan.
Jeffrey S. Perez was supported by the Japanese Government
(Monbukagusho) Scholarship and the Philippine Institute of Volcanology and Seismology – Department of Science and Technology
(PHIVOLCS-DOST). We are grateful to Mabelline Cahulogan, Desiderio
Cabanlit, Daisuke Ishimura and Edwin Ariola for their assistance during
the paleoseismic trenching studies and field mapping. We thank the local government units of the Municipality of Santiago and Butuan City for
logistic support and coordination to conduct the field work in these
areas. We especially express our gratitude to Mrs. Eugenia Morada,
Mr. Ponciano Apat and their families for their generous hospitality and
for allowing us to conduct trench excavations in their properties.
References
Allen, C.R., 1962. Circum-Pacific faulting in Philippines-Taiwan region. J. Geophys. Res. 67
(12):4795–4812. http://dx.doi.org/10.1029/JZ067i012p04795.
Aurelio, M.A., 2000. Shear partitioning in the Philippines: constraints from Philippine fault
and global positioning system data. Island Arc 9 (4):584–597. http://dx.doi.org/10.
1111/j.1440-1738.2000.00304.x.
Aurelio, M., Barrier, E., Rangin, C., Muller, C., 1991. The Philippine fault in the Late
Cenozoictectonic evolution of the Bondoc-Masbate-N. Leyte area, Central Philippines.
J. SE Asian Earth Sci. 6 (3/4), 221–228.
Barcelona, B.M., 1981. The nature of the faults in the Philippine fault zone. Proc. Symp. 4th
Regional Conference on Geology of Southeast Asia, Taipei, pp. 267–275.
Barrier, E., Huchon, P., Aurelio, M., 1991. Philippine fault: a key for Philippine kinematics.
Geology 19 (1):32–35. http://dx.doi.org/10.1130/0091-7613(1991)019b0032:
PFAKFPN2.3.CO;2.
Bautista, M.L.P., 1999. Seismic Hazard Assessment of the Philippines Using Historical and
Recent Earthquakes. (D.Sc. Dissertation (unpublished)). Kyoto University, Kyoto,
Japan (183 pp).
Bautista, M.L.P., Oike, K., 2000. Estimation of the magnitudes and epicenters of Philippine
historical earthquakes. Tectonophysics 317 (1–2):137–169. http://dx.doi.org/10.
1016/S0040-1951(99)00272-3.
Bischke, R.E., Suppe, J., Delpilar, R., 1990. A new branch of the Philippine Fault System as
observed from aeromagnetic and seismic data. Tectonophysics 183 (1–4):243–264.
http://dx.doi.org/10.1016/0040-1951(90)90419-9.
Bureau of Mines and Geosciences, 1981. Geology and Mineral Resources of the Philippines. Bureau of Mines and Geosciences - Ministry of Natural Resources, Metro Manila, Philippines (406 pp).
Cardwell, R.K., Isacks, B.L., Karig, D.E., 1980. The spatial distribution of earthquakes, focal
mechanism solutions, and subducted lithosphere in the Philippine and northeastern
Indonesian islands. In: Hayes, D.E. (Ed.), The Tectonic and Geologic Evolution of
Southeast Asian Seas and Islands, Part 1. The American Geophysical Union Monograph Vol. 23, pp. 1–35.
Daligdig, J.A., 1997. Recent Faulting and Paleoseismicity Along the Philippine Fault Zone,
North Central Luzon, Philippines. (D.Sc. Dissertation (unpublished)). Kyoto University, Kyoto, Japan (73 pp).
Fitch, T.J., 1972. Plate convergence, transcurrent faults, and internal deformation adjacent
to Southeast Asia and the western Pacific. J. Geophys. Res. 77 (23):4432–4460. http://
dx.doi.org/10.1029/JB077i023p04432.
Galgana, G., Hamburger, M., McCaffrey, R., Corpuz, E., Chen, Q.Z., 2007. Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanisms. Tectonophysics 432 (1–4):63–87. http://dx.doi.org/10.1016/j.tecto.2006.12.001.
Hamburger, M.W., Cardwell, R.K., Isacks, B.L., 1983. Seismotectonics of the northern
Philippine island arc. Am. Geophys. Union Geophys. Monogr. 27, 1–22.
Hamilton, W.B., 1979. Tectonics of the Indonesian region. U. S. Geological Survey Professional Paper. 1078 (345 pp).
Jolivet, L., Faccenna, C., 2000. Mediterranean extension and the Africa-Eurasia collision.
Tectonics 19, 1095–1106.
Knuepfer, P.L.K., 1989. Implications of the characteristics of end-points of historical surface fault ruptures for the nature of fault segmentation. In: Schwartz, D.P., Sibson,
R.H. (Eds.), Fault Segmentation and Controls of Rupture Initiation and Termination.
89–315, pp. 193–228 (U.S. Geol. Surv. Open File Rep.).
McCalpin, J. (Ed.), 2009. Paleoseismology, second ed. Elsevier, California, USA (613 pp).
McClusky, S., Balassanian, S., Barka, A., et al., 2000. Global positioning system constraints
on plate kinematics and dynamics in the eastern Mediterranean and Caucasus.
J. Geophys. Res. 105, 5695–5719.
Moore, G.F., Silver, E.A., 1983. Collision processes in the northen Molucca Sea. In: Hayes,
D.E. (Ed.), The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands:
Part 2. American Geophysical Union Monograph Vol. 27, pp. 360–372.
Morante, E.M., 1974. The Ragay Gulf earthquake of March 17, 1973, Southern Luzon, Philippines. J. Geol. Soc. Philipp. 28 (2), 1–31.
Nakata, T., Sangawa, A., Hirano, S., 1977. A report on tectonic landforms along the
Philippine fault zone in Northern Luzon, Philippines. Sci. Rep. 27 (2), 69–93 (Tohoku
University, 7th Series (Geography), Sendai, Japan).
Nakata, T., Tsutsumi, H., Punongbayan, R.S., Rimando, R.E., Daligdig, J.A., Daag, A.S., Besana,
G.M., 1996. Surface fault ruptures of the 1990 Luzon earthquake, Philippines, Special
Publication 25. Research Center for Regional Geography. Hiroshima University, Hiroshima, Japan (86 pp).
Nelson, A.R., Personius, S.F., Rimando, R.E., Punongbayan, R.D., Tuñgol, N., Mirabueno, H.,
Rasdas, A., 2000. Multiple large earthquakes in the pst 1500 years on a fault in Metropolitan Manila, the Philippines. Bull. Seismol. Soc. Am. 90 (1), 73–85.
Ohkura, T., Tabei, T., Kimata, F., Bacolcol, T.C., Nakamura, Y., Luis, A.C., Pelicano, A., Jorgio,
R., Tabigue, M., Abrahan, M., Jorgio, E., Gunawan, E., 2015. Plate convergence and
block motions in Mindanao Island, Philippines as derived from campaign GPS observations. J. Disaster Res. 10 (1), 59–66.
J.S. Perez, H. Tsutsumi Tectonophysics 699 (2017) 244–257
Okubo, P.G., Aki, K., 1987. Fractal geometry in the San Andreas fault system. J. Geophys.
Res. 92, 345–355.
Papiona, K.L., Kinugasa, Y., 2008. Trenching surveys along the Masbate segment of the
Philippine fault zone. J. Geol. Soc. Philipp. 64, 19–53.
Perez, J.S., Tsutsumi, H., 2011. Paleoseismic studies along the Philippine fault zone, eastern
Mindanao, Philippines. Proc. Sym. Japan Geoscience Union Meeting. 2011.
Perez, J.S., Tsutsumi, H., Cahulogan, M.T.C., Cabanlit, D.P., Abigania, M.I.T., Nakata, T., 2015.
Fault distribution, segmentation and earthquake generation potential of the
Philippine fault in eastern Mindanao, Philippines. J. Disaster Res. 10 (1), 74–82.
Philippine Institute of Volcanology and Seismology (PHIVOLCS), 2012C. Earthquake Catalogue From 2007 to 2012.
PHIVOLCS Quick Response Team, 2003. The 15 February 2003 Masbate earthquake report
of investigation. PHIVOLCS Special Report No. 5 (30 pp).
Pinet, N., Stephan, J.F., 1990. The Philippine wrench fault system in the Ilocos Foothills,
Northwestern Luzon, Philippines. Tectonophysics 183 (1–4), 207–224.
Pinet, N., Cobbold, P.R., 1992. Experimental insights into the partitioning of motion within
zones of oblique subduction. Tectonophysics 206 (3–4), 371–388.
Pubellier, M., Quebral, R., Rangin, C., Deffontaines, B., Muller, C., Butterlin, J., Manzano, J.,
1991. The Mindanao collision zone: a soft collision event within a continuous Neogene strike-slip setting. J. SE Asian Earth Sci. 6 (3/4):239–248. http://dx.doi.org/10.
1016/0743-9547(91)90070-E.
Pubellier, M., Quebral, R., Deffontaines, B., Rangin, C., 1993. Neotectonic Map of Mindanao.
Asia Geodynamics Company, Quezon City, Philippines.
Quebral, R.D., Pubellier, M., Rangin, C., 1996. The onset of movement on the Philippine
fault in eastern Mindanao: a transition from a collision to a strike-slip environment.
Tectonics 15 (4), 713–726.
Ramsey, C.B., 1995. Radiocarbon calibration and analysis of stratigraphy: the OxCal program. Radiocarbon 37 (2), 425–430.
Rangin, C., Le Pichon, X., Mazzotti, S., Pubellier, M., Chamot-Rooke, N., Aurelio, M.,
Walpersdorf, A., Quebral, R., 1999. Plate convergence measured by GPS across the
Sundaland/Philippine sea plate deformed boundary: the Philippines and eastern Indonesia. Geophys. J. Int. 139 (2):296–316. http://dx.doi.org/10.1046/j.1365-246x.
1999.00969.x.
Reimer, P.J., Baillie, M.G.L., Bard, E., et al., 2009. IntCal09 and Marine09 radiocarbon age
calibration curves, 0–50000 years cal BP. Radiocarbon 51, 1111–1150.
Repetti, W.C., 1946. Catalogue of Philippine earthquakes, 1589–1899. Bull. Seismol. Soc.
Am. 36 (3), 133–322.
Ringenbach, J.C., Pinet, N., Stephan, J.F., Delteil, J., 1993. Structural variety and tectonic
evolution of strike-slip basins related to the Philippine Fault System, Northern
Luzon, Philippines. Tectonics 12 (1), 187–203.
257
Rutland, R.W.R., 1968. A tectonic study of part of the Philippine fault zone. Q. J. Geol. Soc.
Lond. 123, 295–325.
Schwartz, D.P., Coppersmith, K.J., 1984. Fault behavior and chracteristic earthquakes: examples from the Wasatch and San Andreas fault zones. J. Geophys. Res. 89,
5681–5698.
Segall, P., Pollard, P.D., 1980. Mechanics of discontinuous faults. J. Geophys. Res. 85,
4337–4350.
Sibson, R.H., 1985. Stopping of earthquake ruptures at dilational fault jogs. Nature 316,
248–251.
Sieh, K., 1978a. Slip along the San Andreas fault associated with the great 1857
eaarthquake. Bull. Seismol. Soc. Am. 68, 1421–1448.
Sieh, K., 1978b. Pre-historic large earthquakes produced by slip on the San Andreas fault
at Pallett Creek, California. J. Geophys. Res. 83, 3907–3939.
Sieh, K.E., Jahns, R.H., 1984. Behavior of the southernmost San Andreas fault during the
past 300 years. J. Geophys. Res. 95, 6629–6645.
Sieh, K.E., Williams, P.L., 1990. Holocene activity of the San Andreas fault at Wallace Creek,
California. Bull. Geol. Soc. Am. 95, 883–896.
Sieh, K., Natawidjaja, D., 2000. Neotectonics of the Sumatran fault, Indonesia. J. Geophys.
Res. 105, 28295–28326.
Southeast Asia Association of Seismology and Earthquake Engineering (SEASEE), 1985g.
Catalogue of Philippine earthquakes. Series of Seismology (Philippines) IV (843 pp).
Sylvester, A.G., 1988. Strike-slip faults. Geol. Soc. Am. Bull. 100, 1666–1703.
Tsutsumi, H., Daligdig, J.A., Goto, H., Tungol, N.M., Kondo, H., Nakata, T., Okuno, M., Sugito,
N., 2006. Timing of Surface-Rupturing Earthquakes on the Philippine Fault Zone in
Central Luzon Island. American Geophysical Union, Philippines. EOS Transactions,
p. 52.
Tsutsumi, H., Perez, J.S., 2013. Large-scale digital mapping of the Philippine fault zone
based on aerial photograph interpretation. Active Faults Research. 39, pp. 29–37.
Tsutsumi, H., Perez, J.S., Marjes, J.U., Papiona, K.L., Ramos, N.T., 2015. Coseismic displacement and recurrence interval of the 1973 Ragay Gulf earthquake, southern Luzon,
Philippines. J. Disaster Res. 10 (1), 83–90.
Tsutsumi, H., Okada, A., 1996. Segmentation and Holocene surface faulting on the Median
Tectonic Line, southwest Japan. J. Geophys. Res. 101, 5855–5871.
Wells, D.L., Coppersmith, K.J., 1994. New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bull. Seismol. Soc.
Am. 84 (4), 974–1002.
Wesnousky, S.G., 2006. Predicting the endpoints of earthquake ruptures. Nature 444,
358–360.