The Pegasus Bay aftershock sequence of the Mw 7.1 Darfield (Canterbury), New Zealand earthquake

Abstract. Current models to explain regional-scale landslide events are not able to account for the possible effects of the legacy of previous earthquakes, which have triggered landslides in the past and are known to drive damage accumulation in brittle hillslope materials. This paper tests the hypothesis that spatial distributions of earthquake-induced landslides are determined by both the conditions at the time of the triggering earthquake (time-independent factors) and the legacy of past events (time-dependent factors). To explore this, we under\\-take an analysis of failures triggered by the 1929 Buller and 1968 Inangahua earthquakes, in the northwest South Island of New Zealand. The spatial extents of landslides triggered by these events were in part coincident. Spatial distributions of earthquake-triggered landslides are determined by a combination of earthquake and local characteristics, which influence the dynamic response of hillslopes. To identify the influence of a legacy from past events, we first use logistic regression to control for the effects of time-independent variables. Through this analysis we find that seismic ground motion, hillslope gradient, lithology, and the effects of topographic amplification caused by ridge- and slope-scale topography exhibit a consistent influence on the spatial distribution of landslides in both earthquakes. We then assess whether variability unexplained by these variables may be attributed to the legacy of past events. Our results suggest that hillslopes in regions that experienced strong ground motions in 1929 were more likely to fail in 1968 than would be expected on the basis of time-independent factors alone. This effect is consistent with our hypothesis that unfailed hillslopes in the 1929 earthquake were weakened by damage accumulated during this earthquake and its associated aftershock sequence, which influenced the behaviour of the landscape in the 1968 earthquake. While our results are tentative, they suggest that the damage legacy of large earthquakes may persist in parts of the landscape for much longer than observed sub-decadal periods of post-seismic landslide activity and sediment evacuation. Consequently, a lack of knowledge of the damage state of hillslopes in a landscape potentially represents an important source of uncertainty when assessing landslide susceptibility. Constraining the damage history of hillslopes, through analysis of historical events, therefore provides a potential means of reducing this uncertainty.

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Foreshocks and delayed triggering of the 2016 MW7.1 Te Araroa earthquake and dynamic reinvigoration of its aftershock sequence by the MW7.8 Kaikōura earthquake, New Zealand

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2017.11.020 ◽

2018 ◽

Vol 482 ◽

pp. 265-276 ◽

Cited By ~ 8

Author(s):

Emily Warren-Smith ◽

Bill Fry ◽

Yoshihiro Kaneko ◽

Calum J. Chamberlain

Keyword(s):

New Zealand ◽

Aftershock Sequence ◽

Kaikoura Earthquake

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Aftershock sequence parameters in New Zealand

Bulletin of the Seismological Society of America ◽

10.1785/bssa0880041095 ◽

1998 ◽

Vol 88 (4) ◽

pp. 1095-1097

Author(s):

Donna Eberhart-Phillips

Keyword(s):

New Zealand ◽

Aftershock Sequence ◽

Magnitude Distribution ◽

Generic Models ◽

Earthquake Sequences ◽

Sequence Parameters ◽

Aftershock Hazard

Abstract Regional generic models describing the temporal and magnitude distribution of aftershocks are routinely used in California to assess aftershock hazard. This note applies the Reasenberg and Jones (1989) formulation of aftershock parameters to 17 New Zealand earthquake sequences of M ≧ 5.5, from 1987 through 1995. The median values of the aftershock parameters are similar to those obtained for California.

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The Darfield (Canterbury) earthquake of September 2010

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.43.4.215-221 ◽

2010 ◽

Vol 43 (4) ◽

pp. 215-221 ◽

Cited By ~ 38

Author(s):

Ken Gledhill ◽

John Ristau ◽

Martin Reyners ◽

Bill Fry ◽

Caroline Holden

Keyword(s):

New Zealand ◽

Slip Surface ◽

Moment Tensor ◽

Surface Expression ◽

Aftershock Sequence ◽

Heavy Load ◽

Internet Age ◽

First Motion ◽

Vertical Accelerations ◽

Fault Trace

The Darfield moment magnitude (Mw) 7.1 earthquake of September 2010 is the first heavily damaging earthquake to strike New Zealand since the surface wave magnitude (MS) 7.8 Hawkes Bay earthquake in 1931. Although the earthquake has a clear strike-slip surface expression characterised by the Greendale Fault, seismological evidence suggests it is a complex event beginning as a reverse faulting earthquake. Evidence for complexity of the mainshock includes a well constrained epicentre north of the surface fault trace, high near-source vertical accelerations, first-motion and regional moment tensor focal mechanisms which differ from teleseismic solutions, and a complex aftershock pattern. The earthquake and aftershock sequence were very well recorded by the GeoNet sensor networks in the region, and provide an exceptional dataset for understanding the earthquake rupture process and reducing damage from future earthquakes. This was the most significant test of GeoNet since its inception in 2001, and the first such New Zealand event in the “internet age”. GeoNet data proved important for the response and the interaction with emergency management, media and the public. The GeoNet website sustained continued heavy load over the weeks and months following the earthquake but continued to deliver timely information because of significant improvements carried out as the aftershock sequence continued.

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Correlations between solid tides and worldwide earthquakes <i>M</i><sub>S</sub> ≥ 7.0 since 1900

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-587-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 587-590 ◽

Cited By ~ 11

Author(s):

L. Chen ◽

J. G. Chen ◽

Q. H. Xu

Keyword(s):

New Zealand ◽

Solid Earth ◽

Lunar Cycle ◽

Aftershock Sequence ◽

Lunar Periodicity

Abstract. Most studies on the correlations between earthquakes and solid tides mainly concluded the syzygies (i.e. new or full moons) of each lunar cycle have more earthquakes than other days in the month. We show a correlation between the aftershock sequence of the ML = 6.3 Christchurch, New Zealand, earthquake and the diurnal solid tide. Ms ≥ 7 earthquakes worldwide since 1900 are more likely to occur during the 0°, 90°, 180° or 270° phases (i.e. earthquake-prone phases) of the semidiurnal solid earth tidal curve (M2). Thus, the semidiurnal solid tides triggers earthquakes. However, the long-term triggering effect of the lunar periodicity is uncertain. This proposal is helpful in defining possible origin times of aftershocks several days after a mainshock and can be used for warning of subsequent larger shocks.

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Spatial distributions of earthquake-induced landslides and hillslope preconditioning in northwest South Island, New Zealand

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-3-1-2015 ◽

2015 ◽

Vol 3 (1) ◽

pp. 1-52 ◽

Cited By ~ 6

Author(s):

R. N. Parker ◽

G. T. Hancox ◽

D. N. Petley ◽

C. I. Massey ◽

A. L. Densmore ◽

...

Keyword(s):

New Zealand ◽

Regional Scale ◽

Aftershock Sequence ◽

Spatial Distributions ◽

Damage State ◽

Local Characteristics ◽

History Of ◽

Analysis Of Failures ◽

Landslide Distribution ◽

Strong Ground

Abstract. Current models to explain regional-scale landslide events are not able to account for the possible effects of the legacy of previous earthquakes, which have triggered landslides in the past and are known to drive damage accumulation in brittle hillslope materials. This paper tests the hypothesis that spatial distributions of earthquake-induced landslides are determined by both the conditions at the time of the triggering earthquake (time-independent factors), and also the legacy of past events (time-dependent factors). To explore this, we undertake an analysis of failures triggered by the 1929 Buller and 1968 Inangahua earthquakes, in the northwest South Island of New Zealand. The spatial extent of landslides triggered by these events was in part coincident (overlapping). Spatial distributions of earthquake-triggered landslides are determined by a combination of earthquake and local characteristics, which influence the dynamic response of hillslopes. To identify the influence of a legacy from past events, we use logistic regression to control for the effects of time-independent variables (seismic ground motion, hillslope gradient, lithology, and the effects of topographic amplification caused by ridge- and slope-scale topography), in an attempt to reveal unexplained variability in the landslide distribution. We then assess whether this variability can be attributed to the legacy of past events. Our results suggest that the 1929 Buller earthquake influenced the distribution of landslides triggered by the 1968 Inangahua earthquake. Hillslopes in regions that experienced strong ground motions in 1929 were more likely to fail in 1968 than would be expected on the basis of time-independent factors alone. This effect is consistent with our hypothesis that unfailed hillslopes in the 1929 earthquake were weakened by damage accumulated during this earthquake and its associated aftershock sequence, and this weakening then influenced the performance of the landscape in the 1968 earthquake. While our results are tentative, the findings emphasize that a lack of knowledge of the damage state of hillslopes in a landscape potentially represents an important source of uncertainty when assessing landslide susceptibility. Constraining the damage history of hillslope materials, through analysis of historical events, therefore provides a potential means of reducing this uncertainty.

Download Full-text