Paleoearthquake record of the Conway segment of the Hope fault: Implications for patterns of earthquake occurrence in northern South Island and southern North Island, New Zealand

Alexandra E. Hatem, James F. Dolan, Robert M. Langridge, Robert W. Zinke, Russ J. Van Dissen, Christopher P. McGuire, & Ed J. Rhodes

Submitted August 10, 2018, SCEC Contribution #8382, 2018 SCEC Annual Meeting Poster #221

Paleoseismic trenches excavated at two sites reveal the ages of late Holocene earthquakes along the Conway segment of the Hope fault, the fastest-slipping fault within the Marlborough fault system in northern South Island, New Zealand. At the Green Burn East site (GBE), a fault-perpendicular trench exposed gravel colluvial wedges, fissure fills, and upward fault terminations associated with five, and possibly six, paleo-surface ruptures. Radiocarbon age constraints indicate that these six earthquakes have occurred during the past 2,000 years, with the three most recent surface ruptures occurring during a relatively brief (< 350 year) period between c. 1500 CE and the beginning of the historical earthquake record c.1840 CE. Additional trenches excavated at the Green Burn West site (GBW) site 1.4 km to the west reveal four coseismically generated landslides that occurred at approximately the same times as the four most recent GBE paleoearthquakes. Combining age constraints from both trench sites reduces dating uncertainties and provides independent age ranges for all events. These new data facilitate comparisons with similar paleoearthquake records from other faults within the Alpine-Hope-Jordan-Kekerengu-Needles-Wairarapa (Al-Hp-JKN-Wr) fault system of through-going, fast slip rate dextral and oblique reverse-dextral faults that accommodate the majority of Pacific-Australia relative plate boundary motion. These comparisons indicate that, although the faults of the Al-Hp-JKN-Wr system commonly rupture in brief sequences that encompass large sections of the system, system-wide “wall-to-wall” rupture sequences involving all faults in the system are rare.



Key Words
paleoseismology, plate boundary strain, Hope fault, New Zealand, Marlborough fault system, strike-slip fault

Citation
Hatem, A. E., Dolan, J. F., Langridge, R. M., Zinke, R. W., Van Dissen, R. J., McGuire, C. P., & Rhodes, E. J. (2018, 08). Paleoearthquake record of the Conway segment of the Hope fault: Implications for patterns of earthquake occurrence in northern South Island and southern North Island, New Zealand. Poster Presentation at 2018 SCEC Annual Meeting.


Related Projects & Working Groups
Earthquake Geology