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Publications
Chen, K. H., Nadeau, R. M., and Rau, R. J. (2007). Towards a universal rule
on the recurrence interval scaling of repeating earthquakes?, Geophys. Res. Lett., 34, L16308, doi:10.1029/2007GL030554. (pdf)
[*chosen as AGU journal editors’ highlight (news)]
J.-C. Hu,, Hou,
C.-S., Shen, L.-C., Chan, Y.-C., Chen, R.-F.,
Huang, C., Rau, R.-J., Chen, K. H.,
Lin, C.-W., Huang, M.-H., Nien, P.-F., (2007).
Fault activity and lateral extrusion inferred from velocity field
revealed by GPS measurements in the Pingtung
area of southwestern Taiwan. J. Asian Earth Sci., 35, 287-302,
doi:10.1016/j.jseaes.2006.07.020.
R. J. Rau, Chen, K. H., and Ching, K. E.
(2007). Repeating earthquakes and seismic potential along the northern
Longitudinal Valley fault of eastern Taiwan, Geophys.
Res. Lett., 34,
L24301, doi:10.1029/2007GL031622. (pdf)
Chen, K. H., S. Toda and Rau, R. J., (2008). A leaping,
triggered sequence along a segmented fault: the 1951 Hualien
– Taitung earthquake sequence in eastern
Taiwan, J. Geophys.
Res., 113, B02304, doi:10.1029/2007JB005048.
(pdf)
Chen, K. H., Nadeau, R. M., and Rau, R. J. (2008). Characteristic repeating microearthquakes on an arc-continent collision
boundary - the Chihshang fault of eastern
Taiwan, Earth Planet. Sci. Lett., 276,
doi:10.1016/j.epsl.2008.09.021. (pdf)
Chen, K. H., Rau, R. J., and Hu, J. C. (2009). Variability of the repeating
earthquakes behavior along the Longitudinal Valley fault zone of eastern
Taiwan, J. Geophys. Res., 114, B05306, doi:10.1029/2007JB005518. (pdf)
Chen, K. H., Bürgmann, R., and Nadeau, R. M.
(2010), Triggering effect of M 4-5 earthquakes on the earthquake cycle of
repeating events at Parkfield, Bull. Seismol.
Soc. Am.,100, 2, doi:10.1785/0120080369 (pdf)
[*highlight in BSSA
tip sheet (news)]
Chen, K. H., Bürgmann, R., Nadeau, R. M., T. Chen,
N. Lapusta (2010), Postseismic
variations in seismic moment and recurrence interval of repeating
earthquakes, Earth Planet. Sci. Lett., 299, 118-125,
doi: 10.1016/j.epsl.2010.08.027. pdf
Chen, K. H., Furumura,
T., Rubinstein, J., and Rau, R. J. (2011), Observations of changes in waveform
character induced by the 1999 Mw7.6 Chi-Chi earthquake, Geophys. Res. Lett., 38,
L23302,
doi:10.1029/2011GL049841.
pdf
J. Rubinstein, Ellsworth, W., Chen, K. H., Uchida, N. (2012), Fixed recurrence and slip
models better predict earthquake behavior than the time- and
slip-predictable model 1: Repeating earthquakes, J. Geophys.
Res., 117, B02306, doi:10.1029/2011JB008724.
Chen, K. H., Burgmann, R., Nadeau, R. M.
(2013), Do earthquakes talk to each other? Triggering and interaction of
repeating sequences at Parkfield, J.
Geophys. Res., 118 (1), 165-182, doi:10.1029/2012JB009486. pdf
Chen, K. H., Kennett, B., Furumura, T.
(2013), High frequency waves guided by subducted
plates underneath Taiwan and their association with seismic intensity
anomalies, J. Geophys. Res., 118 (2), 665-680,
doi:10.1029/2012JB009691. pdf
Lin, D. H., Chen, K. H., Rau,
R. J., Hu, J. C. (2013), The role of a hidden
fault in stress triggering: Stress interactions within the 1935 Mw7.1 Hsinchu-Taichung earthquake sequence in central
Taiwan, Tectonophysics,
http://dx.doi.org/10.1016/j.tecto.2013.04.022.
Chuang, L. Y., Chen, K. H.,
Wech, A., Byrne, T., Peng,
W. (2013), Ambient tremors in a collisional orogenic
belt, submitted to Geophys. Res. Lett.
Collaborators
Ruey-Juin Rau (Department of Earth
Sciences, National Cheng-Kung University, Taiwan)
Jyr-Ching Hu (Department of Geosciences,
National Taiwan University, Taiwan)
Shinji Toda (Disaster Prevention
Research Institute, Kyoto University)
Robert Nadeau (Berkeley
Seismological Lab., UC Berkeley, U.S.)
Roland Burgmann
(Department of Earth and Planetary Science, UC Berkeley, U.S.)
Nadia Lapusta
& Ting Chen (Seismological Lab., Caltech, U.S.)
Justin Rubinstein (USGS)
Takashi Furumura
(Earthquake Research Institute, University of Tokyo, Japan)
Brian Kennett (Research School
of Earth Sciences, Australian National University, Australia)
Brian Kennett’s lecture in NTNU (materials)
1.
Seismic waves (video)
2.
Proving the
interior of the Earth (video)
3.
Elements of
seismic tomography (video)
4.
The global
seismic wavefield (video)
5.
Global seismic
tomography (video)
Wen-Tzong
Liang (IES, Acadamia Sinica,
Taiwan)
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My Recent Projects
Monitoring deep
slip rate using repeating earthquake sequence in Taiwan (2008-2009
papers)
Triggering and
interaction of small repeating earthquakes at Parkfield
(2012 JGR paper)
Change in crustal
properties using M4 repeating earthquakes in Taiwan (2012 GRL poster)
High frequency
waves guided by subducted plates in Taiwan and
their association with ground motion anomalies (2013 JGR paper)
QCN outreach in
Taiwan (news)
Ongoing Projects in my lab
Automatic detection of repeating earthquakes
in Taiwan
Taiwan repeating earthquake catalog website by
Eugene Cheng
Automatic detection of ambient tremors in
Taiwan
Taiwan ambient tremor catalog website by
Lindsay Chung
Characterizing non-volcanic hybrid earthquakes
in Taiwan
Fault healing process on the rupture zone of
the M7.6 Chi-Chi earthquake: Observations from repeating earthquakes
Spatio-temporal association between earthquake
swarms and non-volcanic tremors underneath Central Range, Taiwan
Characterization of subduction
zone guided waves
Triggering
and interaction of repeating earthquakes at Parkfield
[with Roland Burgmann and Bob Nadeau]
The
study of what governs the timing of repeating earthquakes is a key to
understanding the nature of the earthquake cycle and to determining
earthquake hazard, yet the control of the recurrences is not well established.
The large population of characteristically repeating earthquakes at Parkfield provides a unique opportunity to study the
controls of repeating events’ aperiodicity, and how the interaction with nearby earthquakes affect their
recurrence properties. We analyze 242 M -0.4 ~ 3.0 repeating earthquake
sequences to examine the variation of recurrence properties in space and
time. We find that the quasi-periodic repeating sequences (i.e.,
coefficient of variation in recurrence interval less than 0.3) tend to
lie in zones of low seismicity.
These quasi-periodic sequences have a smaller number of larger
events in their immediate vicinity, suggesting that more regular
repeating events are more isolated in space and from perturbing stress
changes. The response of the repeating events and other M>3 events to
the occurrence of large earthquakes provides the clearest documentation
of the interaction process. Accelerations of repeating sequences are
associated with the 2004 Parkfield earthquake
and reflect accelerated aseismic afterslip
surrounding the rupture. The recurrences of repeating sequences are found
to correlate with each other when they are close enough in space.
Spatially clustered repeating sequences show evidence of strong
interaction in time, reflected in temporally clustered event recurrences
and similar recurrence history. The temporal correspondence appears to be
a function of separation distance from nearby repeaters, where the
dependence is evident for the repeaters with similar magnitude. Building
on the above observations, we will be able to develop mechanical models
that test the extent to which fault interaction in the form of static
stress changes and transient postseismic fault
creep produces the observed aperiodicity in the occurrence of these
events, and furthermore, attempt to improve predictions of the times of
future event repeats.
Using
the repeating earthquakes in Parkfield we
established
(1)
The degree of interaction between nearby micro-earthquakes [in
preparation for J .Geophys. Res.]
(2)
Triggering of such events by local M > 4 earthquakes [BSSA, 2010]
(3)
The accelerated recurrence and systematic moment changes of repeating
earthquakes in the aftermath of the 2004 Parkfield
earthquake [EPSL, 2010]
Characteristics
of repeating earthquake sequences in eastern Taiwan
[with Robert Nadeau and Ruey-Juin Rau]
My PhD
dissertation topic is Characteristics of repeating earthquake
sequences in eastern Taiwan (supervisor: Ruey-Juin
Rau). Creeping crustal faults often generate a number of microearthquakes, and less commonly, they may also
produce large earthquakes that rupture the brittle crust. The
Longitudinal Valley Fault in eastern Taiwan characterized by such
behavior has been known to undergo 1-3 cm/yr
surface creep, probably one of the most active creeping thrust faults
known in the world. It gives an excellent opportunity for studying how a
creeping fault can generate large earthquakes. However, due to limited
geodetic coverage in this area, a well resolved picture of fault slip
rates at depth has been lacking. Interferometric
Synthetic Aperture Radar (InSAR) data provides
better spatial sampling of the deformation field, but the nature of landcover and atmospheric condition of this area
complicate the task of obtaining more detailed deformation information.
Study
on repeating earthquakes (i.e., a group of events with nearly identical
waveforms, locations, and magnitudes and thus represents a repeated
rupture of the same patch of fault) has been proposed to infer fault slip
rate at depth. However, it also has its limitation because of the poor
station coverage. In this study, we propose a relatively objective method
to identify repeating events in this particular region. Furthermore, using
these results we aim to answer the following questions:
1)
What are the spatial and temporal distributions of repeating earthquakes
and what are their relationships to
the
distribution of seismicity and large earthquakes on the fault?
2) What is the distribution of deep
creep rates that can be inferred from repeating quakes if they exist?
3) How
does deep fault creep inferred from repeating earthquakes compare with
deep creep determined geodetically?
4) How can the repeating earthquake
distribution, inferred rates, overall seismicity patterns, and large
earthquakes
distributions
be used to improve our understanding of the earthquake potential in this
unique tectonic environment?
The
completeness of this project relies on the collaboration with R. M.
Nadeau in U C Berkeley.
Seismogenesis of Taiwan arc-continent collision
boundary
(with
Shinji Toda and Jyr-Ching Hu)
The
island of Taiwan, situated at the plate boundary zone between the
Eurasian plate (EP) and the Philippine Sea plate (PSP), is one of the
best examples of young and rapidly-growing orogeny due to arc-continent
collision. About 25~30% of
the total plate convergence rate of 82 mm/yr
have been concentrated on the narrow arc-continent collision boundary,
Longitudinal Valley (LV) in eastern Taiwan, which indicates that this
boundary may pose a significant seismic threat. Since it has been undergoing
active tectonic collision, the Longitudinal Valley fault (LVF) is
characterized by active fault segments, high seismic activity, and rapid
surface creep. To understand the seismogenic
processes along the LV, I have been interested in answering:
1)
When and where the significant earthquakes may occur in such a high-angle
reverse fault system?
2) How
earthquakes along this boundary interact, propagate, and inhibit each
other?
3) How
the earthquake interactions affect the stressing state and earthquake
probability in eastern Taiwan?
I
worked with Shinji Toda to study a most destructive earthquake series of
eastern Taiwan that is consisted of 12 M>6 earthquakes and sequential
ruptures along four distinct fault segments along the LVF, where we
explained the leaping, triggered sequence by the rate/state stress
transfer model. I have been also working with Jyr-Ching
Hu to study the segmentation of active fault and its implication to the
evaluation of future earthquakes along the LVF.
Healing
of subsurface damage after the 1999 M7.6 Chi-Chi earthquake
(with
Takashi Furumura, Justin Rubinstein, and Ruey-Juin Rau)
We
observe changes in the waveforms of repeating earthquakes in eastern
Taiwan following the 1999 Mw7.6 Chi-Chi earthquake, while
their recurrence intervals appear to be unaffected. There is a clear
reduction in waveform similarity and velocity changes indicated by
delayed phases at the time of the Chi-Chi event. These changes are
limited to stations in and paths that cross the 70×100 km region surrounding the
Chi-Chi source area, the area where seismic intensity and co-seismic
surface displacements were largest. This suggests that damage at the
near-surface is responsible for the observed waveform changes. Delays are
largest in the late S-wave coda, reaching approximately 120 ms. This corresponds to a path averaged S wave velocity reduction of
approximately 1%. There is also evidence that damage in the fault-zone
caused changes in waveform character at sites in the footwall, where
source-receiver paths propagate either along or across the rupture. The
reduction in waveform similarity persists through the most recent
repeating event in our study (November 15, 2007), indicating that the
subsurface damage induced by the Chi-Chi earthquake did not fully heal
within the first 8 years following the Chi-Chi earthquake.
High
frequency waves guided by the subducted plates
underneath Taiwan
(with Brian Kennett and Takashi Furumura)
 
Energy from seismic events
traveling up a subduction zone is frequently
associated with significant large-amplitude, high-frequency signals with
sustained long coda. Such seismic waves guided by the subducted
plate with high wave velocity and high Q can cause surprisingly large
seismic intensity in the forearc area. In this
study we characterize the guiding behavior of the subducted
Philippine Sea plate (PSP) underneath Taiwan, and investigate their
relationship with anomalous peak ground acceleration (PGA) patterns.
Oblique subduction of Philippine Sea plate
beneath northeast Taiwan complicates the guiding phenomena. Seismic waves
from events deeper than 60 km offshore northern Taiwan reveal wave guide
behavior: large, sustained high-frequency (3-10 Hz) signal in P and S
wave trains. With increasing depth, a low-frequency (< 1 Hz) first
arrival becomes more significant especially for events deeper than 100
km. The time separation between the low-frequency onset and the later
high-frequency arrival slightly increases with depth, while the value
varies with station due to different travel distances in the shallow
crust. The depth
dependent high-frequency content confirms the association with a waveguide effect in the subducting slab rather than localized site
amplification effects. We attempt here to obtain a practicable
quantification scheme to determine the duration of higher frequency
energy, which can be regarded as an indicator of the guiding effect of
the Philippine Sea Plate.
Grid-enabled
earthquake science in high school
(with Wen-Tzong
Liang, Chun-Yen
Chang, and Eric Yen) (2012 AGU poster)
High
Scope Program (HSP) is a long-term project funded by NSC in Taiwan since
2006. It is designed to elevate the quality of science education by means
of incorporating emerging science and technology into the traditional curricula
in senior high schools. Quake-Catcher Network (QCN), a distributed
computing project initiated by Stanford University and UC Riverside,
encourages the volunteers to install the low-cost, novel sensors at home
and school to build a seismic network. To meet both needs, we have
developed a model curriculum that introduces QCN, earthquake science, and
cloud computing into high school classrooms.
Through
professional development workshops, Taiwan cloud-based earthquake science
learning platform, and QCN club on Facebook, we have worked closely with Lan-Yang Girl's Senior High School teachers' team to
design workable teaching plans through a practical operation of seismic
monitoring at home or school.
However, some obstacles to learning appear including QCN
installation/maintain problems, high self-noise of the sensor, difficulty
of introducing earthquake sciences for high school teachers. The
challenges of QCN outreach in Taiwan bring out our future plans: (1)
development of easy, frequently updated, physics-based QCN-experiments
for high school teachers, (2) design of an interactive learning platform
with social networking function for students.
近四年的研究方向主要分以下部分進行。
一、 孕震區上方地震滑動與無震滑動之關係
1. 研究地震重複特性與大地震之間的相依性，應用於斷層帶之變形監測。(震後滑移 vs. 無震滑移)
主要與美國加州大學柏克萊分校地球與行星科學系的Roland Burgmann教授和地震研究中心(Berkeley Seismological Lab)研究員 Robert
Nadeau合作，以大量微地震資料分析地震間的觸發行為及其觸發機制。地震能不能以同等規模在同一個地點破裂、以甚麼週期特性展現，受其本身震源特性(破裂範圍內無震滑移所佔的比例)與局部斷層滑移特性(滑移速率、地震空間分布)影響甚鉅。利用美國加州高精度井下地震站收集之重複微地震資料，本人近幾年已發表成果如下:
量化微地震重複特性與中規模以上地震的觸發關係。我們發現規模四以上地震，能影響附近微地震的重複週期，其影響空間範圍與地震規模成非線性關係，而觸發行為的控制機制為震間距離與中規模以上地震之地震矩能量，屬靜態應力觸發之範疇。
利用速率-狀態摩擦定律整合入地震模型，能描述地震聚焦、動態破裂傳播、級瞬間地震滑動和蠕變。與美國加州理工機械工程與地球物理系Nadia Lapusta (及其博士班學生Ting Chen)合作，配合加州微地震觀測，我們發現不同於以往研究室摩擦行為實驗之結果:『等待時間越久、下次破裂發生之規模越大』。我們的重複地震觀測顯示完全相反之趨勢，亦即，受到鄰近大地震的應力變化擾動後，小地震重複週期瞬間加速（週期變短至數天、數月不等，隨離擾動時間越遠，週期逐漸拉長），此時重複地震規模反而變大。此趨勢被發現與地震本身的大小與其斷層面上凹凸体(asperity)的無震滑移比例有關。
2. 結合有限元震波模擬，研究波傳特性在時間空間上的變異，理解斷層復原特性。 (地震滑移)
重複地震的波形高度相似，因為他們發生在同一地點、傳播路徑高度相仿。大地震後，地殼介質特性遽變，可在某些傳播方向的測站被記錄到，形成重複地震波形內的微小變異，這種觀測波形可提供地殼特性時空變化的約制。
以有限差分波傳模擬，配合特殊地震之觀測波形，本人與日本東京大學地震研究所教授Takashi Furumura合作研究震波傳播路徑上的時間、空間變異性，以理解大地震後地殼特性隨時間的復原程度。
3. 利用隱沒帶導波探討台灣下方隱沒帶特性及其與強地動異常之關係。(地震滑移)
經過隱沒板塊的震波具有複雜的波傳特性。當震波在隱沒帶內傳播夠長的距離時，常會產生具有低頻前兆的高頻導波：低頻的P波初達，尾隨以高振幅、持續時間長的高頻訊號。在日本，此種隱沒帶導波造成了弧前盆地的異常高震度，即使震央在100公里之外、深度大於300 km。這種導波（guided
wave）被視作是評估強地動特性及理解隱沒板塊細部構造的一個重要觀測。台灣位處兩個隱沒板塊交互作用之碰撞縫合帶，東北方有隱沒的菲律賓海板塊，南方外海有隱沒的歐亞大陸板塊。本人和澳洲國立大學地球科學院Brian Kennett教授，以及日本東京大學地震研究所教授Takashi
Furumura針對此研究主題自2009年開始合作，我們發現典型的高頻隱沒帶導波頻繁地出現在台灣北部，影響台灣的強地動特性。
二、 孕震區下方地震滑動與無震滑動之關係
探討上下部地殼尺度的地震觸發行為，並發展長微震事件自動偵測系統，以利地殼深部變形監測 (長微動)
在孕震區更深部的下部地殼，長微震事件(non-volcanic tremor)的發現近年來引起大量關注，這些事件釋放的地震矩能量可對等於規模六的地震事件，因此被視作是地震潛能計算中不可忽略的重點研究。長微震被發現可以受遠距地震表面波的觸發，觸發距離可以長達處百公里，而大地震也在鄰近區域，影響了長微震的頻繁度，說明下部地殼的觸發特徵具有爭議性。
在上部地殼尺度，一般地震的觸發型態為密集的餘震; 特殊的重複地震其觸發型態為縮短的重複週期、規模的微量變動、亦伴隨密集的震後事件; 而在下部地殼尺度，長微震的觸發型態為頻繁的活動、以及與遠距表面波的到時同步。本人與學生量化分析上、下部地殼尺度的觸發行為，並建立自動化偵測系統、大量蒐集台灣的重複地震與長低頻震動事件，以釐清控制長微震活動性之發生特徵和機制。
三、 校園地震科學平台
『小電腦做大科學』
要怎麼樣讓高中、國中甚至國小學生了解地震、動手玩地震? 進而將地震科學大眾化平民化?
我們需要的是 (1) 吸引學生興趣的教學工具
- (2) 不需要教師們具有地震學基礎的學習平台。
在國科會科教處高瞻計畫的支持下，我們和蘭陽女中、中央研究院地科所與網格中心合作，引進『QCN捕震網』的概念，以『人手一台感震器』融入數位學習課程。
學生能將感震器帶回家，親自感受當記錄員的經驗，經由台灣補震網的數位平台，學生們可以學習怎麼與他們即時/累積的地震資料互動，也可學習如何利用雲端科技和同學們分享、處理資料、並學習地震資料所蘊含的科學訊息。本課程能把高中原有教學模組，活化成實際學習經驗，除了融入現行基礎地球科學課程裡的地震科學外，他們將學習到如何將地震科學應用於生活。
本計畫與中研院地球科學所梁文宗博士的團隊密切合作。
徵求地震志工!
地震學園 (知識端)
台灣地震科學雲端學習平台 (技術端)
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