Name: Obara, Kazushige
Division/Center: Center for Geophysical Observation and Instrumentation
Research Area: Observation seismology

Last Update 05/17 2017


Slow earthquakes, defined by anomalously long characteristic time, reflect a different slip regime than fast faulting of regular earthquakes, occur around the megathrust seismogenic zone on the subducting plate interface. The non-volcanic tremor was discovered in southwest Japan at first, then have been detected in some subduction zones. We study the occurrence mechanism of slow earthquakes and development of monitoring method for discovery of new seismic phenomena and precise detection of various slow earthquake activity in order to clarify the relationship between these slow earthquakes and megathrust earthquake.


Obara, K. and T. Maeda, Reverse propagation of T waves from the Emperor seamount chain, Geophys. Res. Lett., 36, L08304, doi:10.1029/2009GL037454, , 2009.

Obara, K., Inhomogeneous distribution of deep slow earthquake activity along the strike of the subducting Philippine Sea Plate, Gondwana Research, 16, 512--526, 2009.

Obara, K. and S. Sekine, Characteristic activity and migration of episodic tremor and slow-slip events in central Japan, Earth Planets Space, 61, 853--862, 2009.

Maeda, T. and K. Obara, Spatiotemporal distribution of seismic energy radiation from low-frequency tremor in western Shikoku, Japan, J. Geophys. Res., 114, B00A09, doi:10.1029/2008JB006043, , 2009.

Ito, Y., K. Obara, T. Matsuzawa and T. Maeda, Very low frequency earthquakes related to small asperities on the plate boundary interface at the locked to aseismic transition, J. Geophys. Res., 114, B00A13, doi:10.1029/2008JB006036, , 2009.

Matsuzawa, T., K. Obara and T. Maeda, Source duration of deep very low frequency earthquakes in western Shikoku, Japan, J. Geophys. Res., 114, B00A11, doi:10.1029/2008JB006044, , 2009.

小原一成, フィリピン海プレート沈み込みに伴う西南日本のスロー地震群の発見, 地震2, 61, S315--S327, 2009.

Obara, K., Phenomenology of deep slow earthquake family in southwest Japan: Spatiotemporal characteristics and segmentation, J. Geophys. Res., 115, B00A25, doi:10.1029/2008JB006048, , 2010.

Obara, K. and M. Matsumura, Reverse Propagation of Surface Waves Reflected from Seamounts in the Northwestern Pacific , Bull. Seism. Soc. Am., 100, 1342--1349, 2010.

Obara, K., T. Maeda, S. Tanaka and T. Matsuzawa, Depth-dependent activity of non-volcanic tremor in southwest Japan, Geophys. Res. Lett., 37, L13306, doi:10.1029/2010GL043679, , 2010.

Aoi, S., B. Enescu, W.Suzuki, Y. Asano, K. Obara, T. Kunugi and K. Shiomi, Stress transfer in the Tokai subduction zone from the 2009 Suruga Bay earthquake in Japan, Nature Geoscience, 3, 496--500, 2010.

Hirose, H. and K. Obara, Recurrence behavior of short-term slow slip and correlated non-volcanic tremor episodes in western Shikoku, southwest Japan, J. Geophys. Res., 115, B00A21, doi:10.1029/2008JB006050, , 2010.

Sekine, S., H. Hirose and K. Obara, Along-strike variations in short-term slow slip events in the southwest Japan subduction zone, J. Geophys. Res., 115, B00A27, doi:10.1029/2008JB006059, , 2010.

Ueno, T., T. Maeda, K. Obara, Y. Asano and T. Takeda, Migration of low frequency tremor revealed from multiple array analyses in western Shikoku, Japan, J. Geophys. Res., 115, B00A26, doi:10.1029/2008JB006051, , 2010.

Kimura, H., T. Takeda, K. Obara and K. Kasahara, Seismic Evidence for Active Underplating Below the Megathrust Earthquake Zone in Japan, Science, 329, 210--212, 2010.

Hirose, H., Y. Asano, K. Obara, T. Kimura, T. Matsuzawa, S. Tanaka and T. Maeda , Slow Earthquakes Linked Along Dip in the Nankai Subduction Zone, Science, 330, 1502, , 2010.

K.Obara, T.Matsuzawa, S.Tanaka, T.Kimura, and T.Maeda, Migration properties of non‐volcanic tremor in Shikoku, southwest Japan, Geophys. Res. Lett., 38, L09311, doi:10.1029/2011GL047110, , 2011.

K.Obara, Characteristics and interactions between non-volcanic tremor and related slow earthquakes in the Nankai subduction zone, southwest Japan, J. Geodynamics, 52, 229--248, 2011.

K.Obara, T.Matsuzawa and S.Tanaka, and T.Maeda, Depth-dependent mode of tremor migration beneath Kii Peninsula, Nankai subduction zone, Geophys. Res. Lett., 39, L10308, doi:10.1029/2012GL051420, , 2012.

K.Obara, New detection of tremor triggered in Hokkaido, northern Japan by the 2004 Sumatra–Andaman earthquake, Geophys. Res. Lett., 39, L20305, doi:10.1029/2012GL053339, , 2012.

Y.Yamashita, H.Yakiwara, Y. Asano, H. Shimizu, K. Uchida, S. Hirano, K. Umakoshi, H. Miyamachi, M. Nakamoto, M. Fukui, M. Kamizono, H. Kanehara, T. Yamada, M. Shinohara, K. Obara, Migrating tremor off southern Kyushu as evidence for slow slip of a shallow subduction interface, Science, 348, 676-679, DOI: 10.1126/science.aaa4242, , 2015.

A.A.Delorey, K.Chao and K.Obara, P.A.Johnson, Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake, Science Advances, 1, e1500468, DOI: 10.1126/sciadv.1500468, , 2015.

K.Chao and K.Obara, Triggered Tectonic Tremor in Various Types of Fault Systems of Japan Following the 2012 Mw8.6 Sumatra Earthquake, J. Geophys. Res., 121, 170-187, 10.1002/2015JB012566, , 2016.

R. Takagi, K.Obara and T.Maeda, Slow slip event within a gap between tremor and locked zones in the Nankai subduction zone, Geophys. Res. Lett., 43, 1066-1074. doi:10.1002/2015GL066987, , 2016.

Annoura, S., K. Obara, and T. Maeda, Total energy of deep low-frequency tremor in the Nankai subduction zone, southwest Japan, Geophys. Res. Lett., 43, 2562–2567, doi:10.1002/2016GL06778, , 2016.

K. Obara and A. Kato, Connecting slow earthquakes to huge earthquakes, Science, 353, (6296), 253-257. doi:10.1126/science.aaf1512, , 2016.

Obara, K., Deep slow earthquake activities in Nankai subduction zone, southwest Japan -Overview and recent topics- , IRIS Workshop, Snowbird, UT (USA), 2010/6/11, , 2010.

Obara, K., Depth-dependent slip regime on the plate interface revealed from slow earthquake activities in the Nankai subduction, EarthScope Workshop, Portlaand, OR(USA), 2010/10/13, , 2010.

K. Obara, Discovery of non-Volcanic tremor and contribution to earth science by NIED Hi-net, AGU 2015 Fall Meeting, San Francisco(USA), 2015/12/14-12/18, S23E-01, , 2015.

小原一成, 短期的スロースリップ・深部低周波微動、地震予知連絡会編「地震予知連絡会40年のあゆみ」, 国土地理院, 2009.

小原一成, 独立行政法人防災科学技術研究所、地震予知連絡会編「地震予知連絡会40年のあゆみ」, 国土地理院, 2009.