scholarly journals The Long Recurrence Intervals of Small Repeating Earthquakes May Be Due to the Slow Slip Rates of Small Fault Strands

2019 ◽  
Vol 46 (22) ◽  
pp. 12823-12832
Author(s):  
J. R. Williams ◽  
J. C. Hawthorne ◽  
O. Lengliné
Keyword(s):  
Slow Slip ◽  
Slip Rates ◽  
Repeating Earthquakes ◽  
Small Fault ◽  
Recurrence Intervals

scholarly journals Repeating Earthquake Detection and Characterisation in New Zealand: A Catalogue for the Raukumara Peninsula, Northern Hikurangi Subduction Margin

2021 ◽  
Author(s):  
◽  
Laura Hughes
Keyword(s):  
New Zealand ◽  
Cross Correlation ◽  
Active Faults ◽  
P Wave ◽  
Slow Slip ◽  
Normal Faulting ◽  
Repeating Earthquakes ◽  
Long Duration ◽  
Recurrence Intervals ◽  
Repeating Earthquake

<p>Repeating earthquakes provide a novel way of monitoring how stresses load faults between large earthquakes. In this thesis, we develop a method and composite criterion for identifying repeating earthquakes in New Zealand and present New Zealand’s first long-duration repeating earthquake catalogue. This thesis addresses three primary objectives: (1) develop a method and composite criterion for identifying repeating earthquakes; (2) build a long-duration catalogue of repeating earthquakes for the Raukumara Peninsula; and (3) apply the method and composite criterion in different tectonic settings to investigate whether it can be applied more broadly elsewhere in New Zealand. The systematic identification of repeating earthquakes in New Zealand provides the first step in being able to monitor the state of stresses of New Zealand’s active faults in situ throughout the earthquake cycle.  Studies elsewhere, particularly in Japan and California, have developed case-specific criteria for identifying repeating earthquakes. Building on these studies, we develop a method and composite criterion for identifying repeating earthquakes in New Zealand, focusing on seismicity around the Raukumara Peninsula. Our composite criterion states that for events to be identified as repeating earthquakes, two or more events must have a normalised cross-correlation of at least 0.95 at two or more seismic stations, when calculated for 75% of the earthquake coda. Sensitivity to correlation window length, filtering frequency-band and correlation threshold were tested during the development of the composite criterion. These tests indicated that small perturbations to the parameter thresholds did not affect our ability to detect repeating earthquakes using the composite criterion.  By applying our composite criterion to seismicity around the Raukumara Peninsula, we identified 62 repeating earthquake families occurring between 2003 and 2018, consisting of 160 individual earthquakes. These families have a magnitude range of MW 1.5–4.5, and have recurrence intervals and family durations of < 1–12 years. High-precision absolute and relative locations were calculated using manual phase picks and cross-correlation re-picking. Focal mechanisms for 56 of the families were also determined, using P-wave first motions, revealing predominantly strike-slip and normal faulting at shallow depths, low-angle reverse faulting along the subduction interface, and normal faulting in the subducting plate. We compared the timing of the repeating earthquakes to slow-slip events previously identified using geodetic measurements around the Raukumara Peninsula and observed that repeating earthquakes occurred during 26 of the 31 identified periods of slow-slip. We also compared the seismic moment– recurrence interval relationship of the Raukumara Peninsula repeating earthquakes to that of earthquakes near Parkfield, California, identified by Nadeau and Johnson (1998), and observed a similar functional relationship. Slip-rates of the Raukumara Peninsula repeating earthquake families were also calculated using a slip-rate–moment relationship and were found to vary from < 10mm/yr to 80mm/yr.  We applied the method and composite criterion developed for the Raukumara Peninsula to two other locations to ensure it could be applied successfully in other New Zealand regions with different seismotectonic characteristics. Using our workflow, we successfully identified four families in Marlborough, and three families around Fiordland. These families differ from those identified around the Raukumara Peninsula in that they had relatively short recurrence intervals and family durations, of 2 minutes– 15 months. The ability of the composite criterion to identify these families confirms its suitability for further studies of repeating earthquakes throughout New Zealand.</p>

scholarly journals Repeating Earthquake Detection and Characterisation in New Zealand: A Catalogue for the Raukumara Peninsula, Northern Hikurangi Subduction Margin

2021 ◽  
Author(s):  
◽  
Laura Hughes
Keyword(s):  
New Zealand ◽  
Cross Correlation ◽  
Active Faults ◽  
P Wave ◽  
Slow Slip ◽  
Normal Faulting ◽  
Repeating Earthquakes ◽  
Long Duration ◽  
Recurrence Intervals ◽  
Repeating Earthquake

<p>Repeating earthquakes provide a novel way of monitoring how stresses load faults between large earthquakes. In this thesis, we develop a method and composite criterion for identifying repeating earthquakes in New Zealand and present New Zealand’s first long-duration repeating earthquake catalogue. This thesis addresses three primary objectives: (1) develop a method and composite criterion for identifying repeating earthquakes; (2) build a long-duration catalogue of repeating earthquakes for the Raukumara Peninsula; and (3) apply the method and composite criterion in different tectonic settings to investigate whether it can be applied more broadly elsewhere in New Zealand. The systematic identification of repeating earthquakes in New Zealand provides the first step in being able to monitor the state of stresses of New Zealand’s active faults in situ throughout the earthquake cycle.  Studies elsewhere, particularly in Japan and California, have developed case-specific criteria for identifying repeating earthquakes. Building on these studies, we develop a method and composite criterion for identifying repeating earthquakes in New Zealand, focusing on seismicity around the Raukumara Peninsula. Our composite criterion states that for events to be identified as repeating earthquakes, two or more events must have a normalised cross-correlation of at least 0.95 at two or more seismic stations, when calculated for 75% of the earthquake coda. Sensitivity to correlation window length, filtering frequency-band and correlation threshold were tested during the development of the composite criterion. These tests indicated that small perturbations to the parameter thresholds did not affect our ability to detect repeating earthquakes using the composite criterion.  By applying our composite criterion to seismicity around the Raukumara Peninsula, we identified 62 repeating earthquake families occurring between 2003 and 2018, consisting of 160 individual earthquakes. These families have a magnitude range of MW 1.5–4.5, and have recurrence intervals and family durations of < 1–12 years. High-precision absolute and relative locations were calculated using manual phase picks and cross-correlation re-picking. Focal mechanisms for 56 of the families were also determined, using P-wave first motions, revealing predominantly strike-slip and normal faulting at shallow depths, low-angle reverse faulting along the subduction interface, and normal faulting in the subducting plate. We compared the timing of the repeating earthquakes to slow-slip events previously identified using geodetic measurements around the Raukumara Peninsula and observed that repeating earthquakes occurred during 26 of the 31 identified periods of slow-slip. We also compared the seismic moment– recurrence interval relationship of the Raukumara Peninsula repeating earthquakes to that of earthquakes near Parkfield, California, identified by Nadeau and Johnson (1998), and observed a similar functional relationship. Slip-rates of the Raukumara Peninsula repeating earthquake families were also calculated using a slip-rate–moment relationship and were found to vary from < 10mm/yr to 80mm/yr.  We applied the method and composite criterion developed for the Raukumara Peninsula to two other locations to ensure it could be applied successfully in other New Zealand regions with different seismotectonic characteristics. Using our workflow, we successfully identified four families in Marlborough, and three families around Fiordland. These families differ from those identified around the Raukumara Peninsula in that they had relatively short recurrence intervals and family durations, of 2 minutes– 15 months. The ability of the composite criterion to identify these families confirms its suitability for further studies of repeating earthquakes throughout New Zealand.</p>

Slow Slip Transients Before the 2011 Tohoku-Oki Earthquake

2014 ◽  
Vol 9 (3) ◽  
pp. 311-316 ◽  
Author(s):  
Aitaro Kato ◽  
◽  
Keyword(s):  
Slow Slip ◽  
Dynamic Rupture ◽  
Geodetic Measurement ◽  
Spatiotemporal Evolution ◽  
Plate Interface ◽  
Slip Rates ◽  
Initiation Point ◽  
Repeating Earthquakes ◽  
Rupture Area ◽  
Foreshock Activity

I review a spatiotemporal evolution of slow-slip transients on the plate interface of the subducting Pacific plate that happened in and around the mainshock rupture area prior to the 2011 Tohoku-Oki earthquake. Based on foreshock activity before the mainshock, two sequences of slow-slip transients were identified by earthquake migrations toward the initiation point of the mainshock rupture. These two slow-slip transients were also detected by geodetic measurement. The second sequence of slow-slip transients, which involved large slip rates, may have caused significant stress loading onto the hypocenter of the mainshock and prompted the initiation of unstable dynamic rupture. In addition, decadal slip-behavior on the plate interface revealed by geodetic measurement and small repeating earthquakes show that slow-slip transients occurred in the down-dip and up-dip portions of the mainshock rupture area. These slow-slip transients imply the reduction of coupling between the subducting and overlying plates, that could be interpreted as the late stage of mega-thrust earthquake cycle, although this notion remains conjectural.

scholarly journals A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: The South Malawi Active Fault Database

2020 ◽  
Author(s):  
Jack N. Williams ◽  
Hassan Mdala ◽  
Åke Fagereng ◽  
Luke N. J. Wedmore ◽  
Juliet Biggs ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Fault ◽  
Slip Rate ◽  
Fault Slip ◽  
Slip Rates ◽  
Scaling Relationships ◽  
Regional Strain ◽  
Earthquake Scaling ◽  
Recurrence Intervals ◽  
Fault Slip Rate

Abstract. Seismic hazard is frequently characterised using instrumental seismic records. However, in regions where the instrumental record is short relative to earthquake repeat times, extrapolating it to estimate seismic hazard can misrepresent the probable location, magnitude, and frequency of future large earthquakes. Although paleoseismology can address this challenge, this approach requires certain geomorphic settings and carries large inherent uncertainties. Here, we outline how fault slip rates and recurrence intervals can be estimated through an approach that combines fault geometry, earthquake-scaling relationships, geodetically derived regional strain rates, and geological constraints of regional strain distribution. We then apply this approach to the southern Malawi Rift where, although no on-fault slip rate measurements exist, there are theoretical and observational constraints on how strain is distributed between border and intrabasinal faults. This has led to the development of the South Malawi Active Fault Database (SMAFD), the first database of its kind in the East African Rift System (EARS) and designed so that the outputs can be easily incorporated into Probabilistic Seismic Hazard Analysis. We estimate earthquake magnitudes of MW 5.4–7.2 for individual fault sections in the SMAFD, and MW 6.0–7.8 for whole fault ruptures. These potentially high magnitudes for continental normal faults reflect southern Malawi's 11–140 km long faults and thick (30–35 km) seismogenic crust. However, low slip rates (intermediate estimates 0.05–0.8 mm/yr) imply long recurrence intervals between events: 102–105 years for border faults and 103–106 years for intrabasinal faults. Sensitivity analysis indicates that the large range of these estimates can be reduced most significantly from an improved understanding of the rate and partitioning of rift-extension in southern Malawi, earthquake scaling relationships, and earthquake rupture scenarios. Hence these are critical areas for future research. The SMAFD provides a framework for using geological and geodetic information to characterize seismic hazard in low strain rate settings with few on-fault slip rate measurements, and could be adapted for use elsewhere in the EARS or globally.

scholarly journals A preliminary catalogue of Hikurangi, New Zealand, Slow Slip Earthquakes, from January 2000 to February 2014

2021 ◽  
Author(s):  
◽  
B. Peter Baxter
Keyword(s):  
New Zealand ◽  
Temporal Evolution ◽  
Processing Route ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Slip Rates ◽  
The North ◽  
General Terms ◽  
Significant Step

<p>This thesis documents processing carried out on cGPS data from 115 sites in the North Island and the top of the South Island of New Zealand in order to produce a catalogue of slow slip events (SSEs) for the Hikurangi Margin covering the period Jan 2000 to Feb 2014. It covers the background to the concept of SSEs and the reporting to date on their occurrence along the Margin, the methods used in the processing and analysis, the results of each significant step, and discussion of the results.  It has been shown that the processing route adopted in this work has reduced the average noise levels in the cGPS data by up to 67%, and has eliminated virtually all correlated (“pink”) noise, thus enabling the detection of small-amplitude events (~ 2mm in cGPS signals).  One hundred and fifty events are catalogued in total, of which 137 are considered likely to be SSEs or similar. The catalogue includes estimates of the uncertainty in each parameter and is thus considered the most comprehensive to date. Sixteen of the inversion results were able to be directly compared with published information and showed satisfactory agreement on location and equivalent moment magnitudes.  The important aspects of the project that have been developed further than has been documented to date in the literature include: partitioning of the secular velocity field over the margin to allow the underlying tectonic signal to be better understood; detailed characterization of the temporal evolution of the SSEs; the identification of approximately 40 events that show slips in the opposite direction to that expected; and some preliminary conclusions concerning event scaling.  One of the objectives of the project was to identify whether there were fundamental differences in the characteristics of SSEs in the northeast and southwest of the margin. On the basis of the analyses to date, it appears that the events form a continuum, at least in terms of depth, temporal evolution, source slip rates and scaling, but in general terms the events in the southwest have been confirmed to be of longer duration than those in the northeast.  The project has identified further work that needs to be carried out or is ongoing in order to maximize the value of these new results.</p>

scholarly journals The impact of earthquake cycle variability on neotectonic and paleoseismic slip rate estimates

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 15-25 ◽  
Author(s):  
Richard Styron
Keyword(s):  
Late Quaternary ◽  
Epistemic Uncertainty ◽  
Slip Rate ◽  
Earthquake Recurrence ◽  
Coseismic Slip ◽  
Slip Rates ◽  
True Value ◽  
Recurrence Intervals ◽  
The Impact ◽  
Earthquake Cycles

Abstract. Because of the natural (aleatoric) variability in earthquake recurrence intervals and coseismic displacements on a fault, cumulative slip on a fault does not increase linearly or perfectly step-wise with time; instead, some amount of variability in shorter-term slip rates results. Though this variability could greatly affect the accuracy of neotectonic (i.e., late Quaternary) and paleoseismic slip rate estimates, these effects have not been quantified. In this study, idealized faults with four different, representative, earthquake recurrence distributions are created with equal mean recurrence intervals (1000 years) and coseismic slip distributions, and the variability in slip rate estimates over 500- to 100 000-year measurement windows is calculated for all faults through Monte Carlo simulations. Slip rates are calculated as net offset divided by elapsed time, as in a typical neotectonic study. The recurrence distributions used are quasi-periodic, unclustered and clustered lognormal distributions, and an unclustered exponential distribution. The results demonstrate that the most important parameter is the coefficient of variation (CV = standard deviation ∕ mean) of the recurrence distributions rather than the shape of the distribution itself. Slip rate variability over short timescales (< 5000 years or 5 mean earthquake cycles) is quite high, varying by a factor of 3 or more from the mean, but decreases with time and is close to stable after ∼40 000 years (40 mean earthquake cycles). This variability is higher for recurrence distributions with a higher CV. The natural variability in the slip rate estimates compared to the true value is then used to estimate the epistemic uncertainty in a single slip rate measurement (as one would make in a geological study) in the absence of any measurement uncertainty. This epistemic uncertainty is very high (a factor of 2 or more) for measurement windows of a few mean earthquake cycles (as in a paleoseismic slip rate estimate), but decreases rapidly to a factor of 1–2 with > 5 mean earthquake cycles (as in a neotectonic slip rate study). These uncertainties are independent of, and should be propagated with, uncertainties in fault displacement and geochronologic measurements used to estimate slip rates. They may then aid in the comparison of slip rates from different methods or the evaluation of potential slip rate changes over time.

scholarly journals Major active faults in Italy: available surficial data

2001 ◽  
Vol 80 (3-4) ◽  
pp. 273-296 ◽  
Author(s):  
Fabrizio Galadini ◽  
Carlo Meletti ◽  
Eutizio Vittori
Keyword(s):  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Eastern Alps ◽  
Southern Apennines ◽  
Slip Rates ◽  
Po Plain ◽  
Fault Parameters ◽  
Recurrence Intervals ◽  
Central Eastern ◽  
Available Information

AbstractAn inventory of the available surficial data on active faults in Italy has been compiled by gathering all the available information on peninsular Italy (project by CNR, National Group for the Defense against Earthquakes), the central-eastern Alps and the Po Plain (EC ‘PALEOSIS’ project). Such information has been summarised in maps (reporting surficial expressions of faults with length L≥11 km) and in a table where fault parameters relevant for seismic hazard assessment (e.g. slip rates, recurrence intervals for surface faulting events, etc..) have been reported. Based on the geological characteristics of the Italian territory, a fault has been considered as active if it shows evidence of Late Pleistocene-Holocene displacements. Active faults in Italy are distributed throughout the entire Apennine chain, in the Sicilian and Calabrian regions and in some Alpine sectors, but knowledge is not homogeneously distributed through the territory. The largest amount of data is related to the central Apennines. In contrast, fault geometries and parameters are less well defined in the southern Apennines, Sicily and Calabria, where investigations have started more recently. Knowledge is sparse in the northern Apeninnes, where data necessary to define fault parameters are lacking and also the chronology of the activity has to be considered cautiously. Abundant blind faulting in the Po Plain hinders the detection of active faults by means of the classical surficial investigations and therefore the present knowledge is limited to the Mantova fault. Blind faults and the peculiar recent geological history of the Alpine areas, which is strongly conditioned by the erosional and depositional activity during and after the last glacial maximum, also hinder the identification of active faults in the central-eastern Alps. Some faults in this Alpine sector are believed to be active, but data on their segmentation are still missing. Available information indicates that Italian active faults are usually characterised by slip rates lower than 1 mm/yr. Recurrence intervals for surface faulting events are longer than 1,000 years in the central and southern Apennines. This review on the Italian active faults represents the first step to produce a map of the major seismic sources in Italy, which in turn will result from the merge of surficial data with seismological and geological subsurficial data. The available knowledge gathered in this paper indicates those areas where data are presently sparse. It should be, therefore, possible to better plan future geomorphological and paleoseismological investigations.

scholarly journals Geologic and geodetic constraints on the seismic hazard of Malawi’s active faults: The Malawi Seismogenic Source Database (MSSD)

2021 ◽  
Author(s):  
Jack N. Williams ◽  
Luke N. J. Wedmore ◽  
Åke Fagereng ◽  
Maximilian J. Werner ◽  
Hassan Mdala ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Fault ◽  
Active Faults ◽  
Slip Rate ◽  
Slip Rates ◽  
Source Database ◽  
Seismogenic Sources ◽  
Seismogenic Source ◽  
Recurrence Intervals ◽  
Seismic Reflector

Abstract. Active fault data are commonly used in seismic hazard assessments, but there are challenges in deriving the slip rate, geometry, and frequency of earthquakes along active faults. Herein, we present the open-access geospatial Malawi Seismogenic Source Database (MSSD), which describes the seismogenic properties of faults that have formed during East African rifting in Malawi. We first use empirical observations to geometrically classify active faults into section, fault, and multi-fault seismogenic sources. For sources in the North Basin of Lake Malawi, slip rates can be derived from the vertical offset of a seismic reflector that is estimated to be 75 ka based on dated core. Elsewhere, slip rates are constrained from advancing a ‘systems-based’ approach that partitions geodetically-derived rift extension rates in Malawi between seismogenic sources using a priori constraints on regional strain distribution in magma-poor continental rifts. Slip rates are then combined with source geometry and empirical scaling relationships to estimate earthquake magnitudes and recurrence intervals, and their uncertainty is described from the variability of outcomes from a logic tree used in these calculations. We find that for sources in the Lake Malawi’s North Basin, where slip rates can be derived from both the geodetic data and the offset seismic reflector, the slip rate estimates are within error of each other, although those from the offset reflector are higher. Sources in the MSSD are 5–200 km long, which implies that large magnitude (MW 7–8) earthquakes may occur in Malawi. Low slip rates (0.05–2 mm/yr), however, mean that the frequency of such events will be low (recurrence intervals ~103–104 years). The MSSD represents an important resource for investigating Malawi’s increasing seismic risks and provides a framework for incorporating active fault data into seismic hazard assessment in other tectonically active regions.

Sign in / Sign up

Export Citation Format

Share Document