The Hikurangi subduction margin, where the Pacific Plate subducts beneath the North Island of New Zealand, poses a major seismic and tsunami hazard to the New Zealand region, but its seismic and tsunami potential is largely unknown because of New Zealand’s short (< 170 years) historical record of seismicity. This article discusses the implications of results from GPS, paleoseismology, and tsunami modeling studies for understanding Hikurangi subduction earthquake and tsunami potential. Paleoseismic and geodetic data indicate that earthquakes of MW 8.0 and larger are certainly plausible at the Hikurangi margin. Paleoseismic evidence for large megathrust earthquakes beneath Hawke Bay in central Hikurangi demonstrates that large seismic slip may occur within an area that currently slips in episodic slow slip events. This result has important implications for seismic hazards at subduction margins elsewhere. Strong similarities between the subduction zones of the Hikurangi margin and the Japan Trench suggest that a giant MW 9.0 earthquake similar to the 2011 Tōhoku-Oki earthquake may be possible for the Hikurangi margin. Such an event would generate a large tsunami that would inundate much of the east coast of the North Island. Understanding of the earthquake potential of the Hikurangi megathrust is only in its infancy, and we recommend a number of studies to increase knowledge.

Wallace, L.M., U.A. Cochran, W.L. Power, and K.J. Clark. 2014. Earthquake and tsunami potential of the Hikurangi subduction thrust, New Zealand: Insights from paleoseismology, GPS, and tsunami modeling. Oceanography 27(2):104–117, https://doi.org/10.5670/oceanog.2014.46.

Ansell, J., and S. Bannister. 1996. Shallow morphology of the subducted Pacific Plate along the Hikurangi margin, New Zealand. Physics of the Earth and Planetary Interiors 93:3–20, https://doi.org/10.1016/0031-9201(95)03085-9.

Barnes, P.M., A. Nicol, and T. Harrison. 2002. Late Cenozoic evolution and earthquake potential of an active listric thrust complex above the Hikurangi subduction zone, New Zealand. Geological Society of America Bulletin 114:1,379–1,405, https://doi.org/10.1130/0016-7606(2002)114<1379:LCEAEP>2.0.CO;2.

Beavan, R.J., and D.J. Darby. 2005. Fault slip in the 1855 Wairarapa earthquake based on new and reassessed vertical motion observations: Did slip occur on the subduction interface? Pp. 31–41 in The 1855 Wairarapa Earthquake Symposium: 150 Years of Thinking About Magnitude 8+ Earthquakes and Seismic Hazard in New Zealand. September 8–10, 2005, Proceedings Volume, Greater Wellington Regional Council, Wellington.

Bell, R., R. Sutherland, D.H.N. Barker, S. Henrys, S. Bannister, L. Wallace, and J. Beavan. 2010. Seismic reflection character of the Hikurangi subduction interface, New Zealand, in the region of repeated Gisborne slow slip events. Geophysical Journal International 180:34–48, https://doi.org/10.1111/j.1365-246X.2009.04401.x.

Berryman, K.R. 1993. Age, height, and deformation of Holocene marine terraces at Mahia Peninsula, Hikurangi subduction margin, New Zealand. Tectonics 12:1,347–1,364, https://doi.org/10.1029/93TC01542.

Berryman, K., Y. Ota, T. Miyauchi, A. Hull, K. Clark, K.I. Ishibashi, Nozomi, and N. Litchfield. 2011. Holocene paleoseismic history of upper-plate faults in the southern Hikurangi Margin, New Zealand, deduced from marine terrace records. Bulletin of the Seismological Society of America 101:2,064–2,087, https://doi.org/10.1785/0120100282.

Chlieh, M., J.P. Avouac, K. Sieh, D.H. Natawidjaja, and J. Galetzka. 2008. Heterogeneous coupling of the Sumatran megathrust constrained by geodetic and paleogeodetic measurements. Journal of Geophysical Research 113, B05305, https://doi.org/10.1029/2007JB004981.

Cisternas, M., B.F. Atwater, F. Torrejón, Y. Sawai, G. Machuca, M. Lagos, A. Eipert, C. Youlton, I. Salgado, T. Kamataki, and others. 2005. Predecessors of the giant 1960 Chile earthquake. Nature 437:404–407, https://doi.org/10.1038/nature03943.

Clague, J.J. 1997. Evidence for large earthquakes at the Cascadia subduction zone. Reviews of Geophysics 35:439–460, https://doi.org/10.1029/97RG00222.

Clark, K.J., B.W. Hayward, U.A. Cochran, H.R. Grenfell, E. Hemphill-Haley, D.C. Mildenhall, M.A. Hemphill-Haley, and L.M. Wallace. 2011. Investigating subduction earthquake geology along the southern Hikurangi margin using palaeoenvironmental histories of intertidal inlets. New Zealand Journal of Geology and Geophysics 54(3):255–271, https://doi.org/10.1080/00288306.2011.562903.

Cochran, U.A., K.R. Berryman, J. Zachariasen, D.C. Mildenhall, B.W. Hayward, K. Southall, C.J. Hollis, P. Barker, L.M. Wallace, B. Alloway, and K. Wilson. 2006. Paleoecological insights into subduction zone earthquake occurrence, eastern North Island, New Zealand. Geological Society of America Bulletin 118:1,051–1,074, https://doi.org/10.1130/B25761.1.

Collot, J.-Y., J. Delteil, K.B. Lewis, B. Davy, G. Lamarche, J.-C. Audru, P. Barnes, F. Chanier, E. Chaumillon, S. Lallemand, and others. 1996. From oblique subduction to intra-continental transpression: Structures of the southern Kermadec-Hikurangi margin from multibeam bathymetry, side-scan sonar and seismic reflection. Marine Geophysical Researches 18:357–381, https://doi.org/10.1007/BF00286085.

Collot, J.-Y., K. Lewis, G. Lamarche, and S. Lallemand. 2001. The giant Ruatoria debris avalanche on the northern Hikurangi margin, New Zealand: Result of oblique seamount subduction. Journal of Geophysical Research 106(B9):19,271–19,297, https://doi.org/10.1029/2001JB900004.

Darby, D., and J. Beavan. 2001. Evidence from GPS measurements for contemporary interplate coupling on the southern Hikurangi subduction thrust and for partitioning of strain in the upper plate. Journal of Geophysical Research 106:30,881–30,891, https://doi.org/10.1029/2000JB000023.

Doser, D.I., and T.H. Webb. 2003. Source parameters of large historical (1917–1961) earthquakes, North Island, New Zealand. Geophysical Journal International 152:795–832, https://doi.org/10.1046/j.1365-246X.2003.01895.x.

Douglas, A., J. Beavan, L. Wallace, and J. Townend. 2005. Slow slip on the northern Hikurangi subduction interface, New Zealand. Geophysical Research Letters 32, L16305, https://doi.org/10.1029/2005GL023607.

Downes, G., T.H. Webb, M.J. McSaveney, C. Chague-Goff, D.J. Darby, and A. Barnett. 2000. The March 25 and May 17 1947 Gisborne earthquakes and tsunami: Implication for tsunami hazard for East Coast, North Island, New Zealand. Pp. 55–67 in Tsunami Risk Assessment Beyond 2000: Theory, Practice and Plans. Proceedings of Joint IOC–IUGG International Workshop, V.K. Gusiakov, B.W. Levin, and O.I. Yakovenko, eds, Moscow.

Dragert, H., K. Wang, and T. James. 2001. A silent slip event on the deeper Cascadia subduction interface. Science 292:1,525–1,528, https://doi.org/10.1126/science.1060152.

Finn, C., G. Kimura, and K. Suyehiro. 1994. Introduction to the special section Northeast Japan: A case history of subduction. Journal of Geophysical Research 99(B11):22,137–22,145, https://doi.org/10.1029/94JB01130.

Fraser, S.A., W.L. Power, X. Wang, L.M. Wallace, C. Mueller, and D.M. Johnston. 2014. Tsunami inundation in Napier, New Zealand, due to local earthquake sources. Natural Hazards 70:415–445, https://doi.org/10.1007/s11069-013-0820-x.

Fujiwara, T., S. Kodaira, T. No, Y. Kaiho, N. Takahashi, and Y. Kaneda. 2011. The 2011 Tohoku-Oki earthquake: Displacement reaching the trench axis. Science 334:1,240.

Gagnon, K., C.D. Chadwell, and E. Norabuena. 2005. Measuring the onset of locking in the Peru–Chile Trench with GPS and acoustic measurements. Nature 434:205–208, https://doi.org/10.1038/nature03412.

Geist, E.L. 2002. Complex earthquake rupture and local tsunamis. Journal of Geophysical Research 107(B5), https://doi.org/10.1029/2000JB000139.

Grapes, R., and G. Downes. 1997. The 1855 Wairarapa, New Zealand, earthquake: Analysis of historical data. Bulletin of the New Zealand National Society for Earthquake Engineering 30(4):271–368.

Hashimoto, C., A. Noda, T. Sagiya, and M. Matsu’ura. 2009. Interplate seismogenic zones along the Kuril–Japan Trench inferred from GPS data inversion. Nature Geoscience 2:141–144, https://doi.org/10.1038/ngeo421.

Hayward, B.W., H.R. Grenfell, A.T. Sabaa, R. Carter, U.A. Cochran, J.H. Lipps, P.R. Shane, and M.S. Morley. 2006. Micropaleontological evidence of large earthquakes in the past 7200 years in southern Hawke’s Bay, New Zealand. Quaternary Science Reviews 25:1,186–1,207, https://doi.org/10.1016/j.quascirev.2005.10.013.

Hayward, B.W., K.J. Wilson, M. Morley, U. Cochran, H.R. Grenfell, A. Sabaa, and R. Daymond-King. 2010. Microfossil record of the Holocene evolution of coastal wetlands in a tectonically active region of New Zealand. The Holocene 30:405–421, https://doi.org/10.1177/0959683609353431.

Henrys, S., A. Wech, R. Sutherland, T. Stern, M. Savage, H. Sato, K. Mochizuki, T. Iwasaki, D. Okaya, A. Seward, and others. 2013. SAHKE geophysical transect reveals crustal and subduction zone structure at the southern Hikurangi margin. Geochemistry, Geophysics, Geosystems 14:2,063–2,083, https://doi.org/10.1002/ggge.20136.

Ide, S., A. Baltay, and G. Beroza. 2011. Shallow dynamic overshoot and energetic deep rupture in the 2011 MW 9.0 Tohoku-Oki earthquake. Science 332:1,426–1,429.

Ito, Y., R. Hino, M. Kido, H. Fujimoto, Y. Osada, D. Inazu, Y. Ohta, T. Iinuma, M. Ohzono, S. Miura, and others. 2013. Episodic slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake. Tectonophysics 600:14–26, https://doi.org/10.1016/j.tecto.2012.08.022.

Ito, Y., T. Tsuji, Y. Osada, M. Kido, D. Inazu, Y. Hayashi, H. Tsushima, R. Hino, and H. Fujimoto. 2011. Frontal wedge deformation near the source region of the 2011 Tohoku‐Oki earthquake. Geophysical Research Letters 38, L00G05, https://doi.org/10.1029/2011GL048355.

Kanamori, H. 1972. Mechanism of tsunami earthquakes. Physics of the Earth and Planetary Interiors 6:346–359, https://doi.org/10.1016/0031-9201(72)90058-1.

King, D.N.T., J. Goff, and A. Skipper. 2007. Māori environmental knowledge and natural hazards in Aotearoa-New Zealand. Journal of the Royal Society of New Zealand 37:59–73, https://doi.org/10.1080/03014220709510536.

Koketsu, K., Y. Yokota, N. Nishimura, Y. Yagi, S. Miyazaki, K. Statake, Y. Fujii, H. Miyake, S. Sakai, Y. Yamanaka, and T. Okada. 2011. A unified source model for the 2011 Tohoku earthquake. Earth and Planetary Science Letters 310:480-487, https://doi.org/10.1016/j.epsl.2011.09.009.

Liu, Y., and J.R. Rice. 2005. Aseismic slip transients emerge spontaneously in three dimensional rate and state modeling of subduction earthquake sequences. Journal of Geophysical Research 110, B08307, https://doi.org/10.1029/2004JB003424.

Loveless, J.P., and B.J. Meade. 2010. Geodetic imaging of plate motions, slip rates, and partitioning of deformation in Japan. Journal of Geophysical Research 115, B02410, https://doi.org/10.1029/2008JB006248.

Loveless, J.P., and B.J. Meade. 2011. Spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 MW = 9.0 Tohoku‐Oki earthquake. Geophysical Research Letters 38, L17306, https://doi.org/10.1029/2011GL048561.

Magloughlin, J.F., and J.G. Spray. 1992. Frictional melting processes and products in geological materials: introduction and discussion. Tectonophysics 204:197–204, https://doi.org/10.1016/0040-1951(92)90307-R.

Mazzotti, S., X. Le Pichon, P. Henry, and S. Miyazaki. 2000. Full interseismic locking of the Nankai and Japan-west Kurile subduction zones: An analysis of uniform elastic strain accumulation in Japan constrained by permanent GPS. Journal of Geophysical Research 105(B6):13,159–13,177, https://doi.org/10.1029/2000JB900060.

McCaffrey, R. 2008. Global frequency of magnitude 9 earthquakes. Geology 36(3):263–266, https://doi.org/10.1130/G24402A.1.

McFadgen, B.G. 2008. Hostile Shores: Catastrophic Events in Prehistoric New Zealand and Their Impact on Maori Coastal Communities. Auckland University Press.

McSaveney, M.J., I.J. Graham, J.G. Begg, A.G. Beu, A.G. Hull, K. Kim, and A. Zondervan. 2006. Late Holocene uplift of beach ridges at Turakirae Head, south Wellington coast, New Zealand. New Zealand Journal of Geology and Geophysics 49:337–358, https://doi.org/10.1080/00288306.2006.9515172.

Miura, S., Y. Suwa, A. Hasegawa, and T. Nishimura. 2004. The 2003 M8.0 Tokachi‐Oki earthquake: How much has the great event paid back slip debts? Geophysical Research Letters 31, L05613, https://doi.org/10.1029/2003GL019021.

Moreno, M., M. Rosenau, and O. Oncken. 2010. 2010 Maule earthquake slip correlates with pre‐seismic locking of Andean subduction zone. Nature 467:198–202, https://doi.org/10.1038/nature09349.

Mortimer, N., and D. Parkinson. 1996. Hikurangi Plateau: A Cretaceous large igneous province in the southwest Pacific Ocean. Journal Geophysical Research 101(B1):687–696, https://doi.org/10.1029/95JB03037.

Mountjoy, J.J., and P.M. Barnes. 2011. Active upper plate thrust faulting in regions of low plate interface coupling, repeated slow slip events, and coastal uplift: Example from the Hikurangi Margin, New Zealand. Geochemistry, Geophysics, Geosystems 12, Q01005, https://doi.org/10.1029/2010GC003326.

Nishimura, T., T. Hirasawa, S. Miyazaki, T. Sagiya, T. Tada, S. Miura, and K. Tanaka. 2004. Temporal change of interplate coupling in northeastern japan during 1995–2002 estimated from continuous GPS observations. Geophysical Journal International 157:901–916, https://doi.org/10.1111/j.1365-246X.2004.02159.x.

Polissar, P.J., H.M. Savage, and E.E. Brodsky. 2011. Extractable organic material in fault zones as a tool to investigate frictional stress. Earth and Planetary Science Letters 311:439–447, https://doi.org/10.1016/j.epsl.2011.09.004.

Pondard, N., and P.M. Barnes. 2010. Structure and paleoearthquake records of active submarine faults, Cook Strait, New Zealand: Implications for fault interactions, stress loading, and seismic hazard. Journal Geophysical Research 115, B12320, https://doi.org/10.1029/2010JB007781.

Power, W.L. (compiler). 2013. Review of Tsunami Hazard in New Zealand (2013 Update). GNS Science Consultancy Report 2013/131, 222 pp.

Power, W., and E. Tolkova. 2013. Forecasting tsunamis in Poverty Bay, New Zealand, with deep-ocean gauges. Ocean Dynamics 63:1,213–1,232, https://doi.org/10.1007/s10236-013-0665-6.

Power, W.L., L. Wallace, and M. Reyners. 2008. Tsunami Hazard Posed by Earthquakes on the Hikurangi Subduction Zone Interface. GNS Science Consultancy Report 2008/40. http://www.eqc.govt.nz/sites/public_files/1600-tsunami-hazard-Hikurangi-subduction-zone-interface.pdf.

Pouderoux, H., J.-N. Proust, and G. Lamarche. 2014. Submarine paleoseismology of the northern Hikurnagi subduction margin of New Zealand as deduced form Turbidite records since 16 ka. Quaternary Science Reviews 84:116–131, https://doi.org/10.1016/j.quascirev.2013.11.015.

Protti, M., V. González, A.V. Newman, T.H. Dixson, S.Y. Schwartz, J.S. Marshall, L. Feng. J.I., Walter, R. Maiservisi, and S.E. Owen. 2014. Nicoya earthquake rupture anticipated by geodetic measurement of the locked plate interface. Nature Geoscience 7:117–121, https://doi.org/10.1038/ngeo2038.

Saffer, D., P. Barnes, L. Wallace, S. Henrys, M. Underwood, M. Torres, and the Hikurangi Margin Working Group. 2011. Unlocking the secrets of slow slip by drilling at the northern Hikurangi subduction margin, New Zealand: Riserless drilling to sample and monitor the forearc and subduction plate. IODP proposal 781A-Full, http://www.iodp.org/700.

Sakaguchi, A., F. Chester, D. Curewitz, O. Fabbri, D. Goldsby, G. Gaku, C.-F. Li, Y. Masaki, E.J. Screaton, A. Tsutsumi, and others. 2011. Seismic slip propagation to the updip end of plate boundary subduction interface faults: Vitrinite reflectance geothermometry on Integrated Ocean Drilling Program NanTroSEIZE cores. Geology 39:395–398, https://doi.org/10.1130/G31642.1.

Satake, K., and B.F. Atwater. 2007. Long-term perspectives on Giant earthquakes and tsunamis at subduction zones. Annual Review of Earth and Planetary Sciences 35:349–374, https://doi.org/10.1146/annurev.earth.35.031306.140302.

Sato, M., T. Ishikawa, N. Ujihara, S. Yoshida, M. Fujita, M. Mochizuki, and A. Asada. 2011. Displacement above the hypocenter of the 2011 Tohoku-Oki earthquake. Science 332:1,395, https://doi.org/10.1126/science.1207401.

Sawai, Y., and H. Nasu. 2005. A 4500-year record of emergence events at Onnetoh, Hokkaido, northern Japan, reconstructed using plant macrofossils. Marine Geology 217(1):49–65, https://doi.org/10.1016/j.margeo.2005.02.006.

Schwartz, S.Y. and J.M. Rokosky. 2007. Slow slip events and seismic tremor at circum-Pacific subduction zones. Reviews of Geophysics 45, RG3004, https://doi.org/10.1029/2006RG000208.

Shennan, I., and S. Hamilton. 2006. Coseismic and pre-seismic subsidence associated with great earthquakes in Alaska. Quaternary Science Reviews 25:1–8, https://doi.org/10.1016/j.quascirev.2005.09.002.

Simons, M., S.E. Minson, A. Sladen, F. Ortega, J. Jiang, S.E. Owen, L. Meng, J.-P. Ampuero, S. Wei, R. Chu, and others. 2011. The 2011 magnitude 9.0 Tohoku-Oki earthquake: Mosaicking the megathrust from seconds to centuries. Science 332: 1,421–1,425, https://doi.org/10.1126/science.1206731.

Suwa, Y., S. Miura, A. Hasegawa, T. Sato, and K. Tachibana. 2006. Interplate coupling beneath NE Japan inferred from three-dimensional displacement field. Journal of Geophysical Research 111, B04402, https://doi.org/10.1029/2004JB003203.

von Huene, R., and S. Lallemand. 1990. Tectonic erosion along the Japan and Peru convergent margins. Geological Society of America Bulletin 102:704–720, https://doi.org/10.1130/0016-7606(1990)102<0704:TEATJA>2.3.CO;2.

Wallace, L.M., P. Barnes, R.J. Beavan, R.J. Van Dissen, N.J. Litchfield, J. Mountjoy, R.M. Langridge, G. Lamarche, and N. Pondard. 2012a. The kinematics of a transition from subduction to strike-slip: An example from the central New Zealand plate boundary. Journal Geophysical Research 117, B02405, https://doi.org/10.1029/2011JB008640.

Wallace, L.M., and J. Beavan. 2010. Diverse slow slip behavior at the Hikurangi subduction margin, New Zealand. Journal of Geophysical Research 115, B12402, https://doi.org/10.1029/2010JB007717.

Wallace, L.M., J. Beavan, S. Bannister, and C. Williams. 2012b. Simultaneous long-term and short-term slow slip events at the Hikurangi subduction margin, New Zealand: Implications for processes that control slow slip event occurrence, duration, and migration. Journal Geophysical Research 117, B11402, https://doi.org/10.1029/2012JB009489.

Wallace, L.M., J. Beavan, R. McCaffrey, and D. Darby. 2004. Subduction zone coupling and tectonic block rotations in the North Island, New Zealand. Journal of Geophysical Research 109, B12406, https://doi.org/10.1029/2004JB003241.

Wallace, L.M., J. Beavan, S. Miura, and R. McCaffrey. 2009b. Using Global Positioning System data to assess tectonic hazards. Pp. 156–175 in Volcanism, Tectonism and Siting of Nuclear Facilities. C. Connor, L. Connor, and N. Chapman, eds, Cambridge University Press.

Wallace, L.M., and D. Eberhart-Phillips. 2013. Newly observed, deep slow slip events at the central Hikurangi margin, New Zealand: Implications for downdip variability of slow slip and tremor, and relationship to seismic structure. Geophysical Research Letters 40:5,393–5,398, https://doi.org/10.1002/2013GL057682.

Wallace, L.M., M. Reyners, U. Cochran, S. Bannister, P.M. Barnes, K. Berryman, G. Downes, D. Eberhart-Phillips, A. Fagereng, S. Ellis, and others. 2009a. Characterizing the seismogenic zone of a major plate boundary subduction thrust: Hikurangi Margin, New Zealand. Geochemistry, Geophysics, Geosystems 10, Q10006, https://doi.org/10.1029/2009GC002610.

Wallace, L.M., Y. Ito, S. Henrys, P. Barnes, D. Saffer, S. Kodaira, H. Tobin, M. Underwood, N. Bangs, A. Fagereng, and others. 2013. Unlocking the secrets of slow slip by drilling at the northern Hikurangi subduction margin, New Zealand: Riser drilling to intersect the plate interface. IODP proposal 781B-Full, http://www.iodp.org/700.

Wang, X., and P.L.F. Liu. 2006. An analysis of 2004 Sumatra earthquake fault plane mechanisms and Indian Ocean tsunami. Journal of Hydraulic Research 44:147–154, https://doi.org/10.1080/00221686.2006.9521671.

Wang, X., G. Prasetya, W.L. Power, B. Lukovic, H. Brackley, and K.R. Berryman. 2009. Gisborne District Council Tsunami Inundation Study. GNS Science Consultancy Report, 233 pp., http://www.gdc.govt.nz/assets/Strategies/Wainui-Beach-Management/Tsunami-Inundation-Study-pgs-1-19.pdf.

Webb, T.H., and H. Anderson. 1998. Focal mechanisms of large earthquakes in the North island of New Zealand: Slip partitioning at an oblique active margin. Geophysical Journal International 134:40–86, https://doi.org/10.1046/j.1365-246x.1998.00531.x.

Williams, C.A., D. Eberhart-Phillips, S. Bannister, D.H.N. Barker, S. Henrys, M. Reyners, and R. Sutherland. 2014. Revised interface geometry for the Hikurangi subduction zone, New Zealand. Seismological Research Letters 84:1,066–1,073, https://doi.org/10.1785/0220130035.

Wilson, K., K. Berryman, N. Litchfield, and T. Little. 2006. A revision of mid-late Holocene marine terrace distribution and chronology at the Pakarae River mouth, North Island, New Zealand. New Zealand Journal of Geology and Geophysics 49:477–489, https://doi.org/10.1080/00288306.2006.9515182.

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.