scholarly journals Upper Plate Structure and Tsunamigenic Faults near the Kodiak Islands

2021 ◽  
Author(s):  
Marlon Ramos ◽  
Lee Liberty ◽  
Peter Haeussler ◽  
Robert Humphreys
Keyword(s):  
Fault Zone ◽  
Source Region ◽  
Earthquake Hazard ◽  
Tsunami Source ◽  
Tsunami Modelling ◽  
Plate Structure ◽  
Rupture Area ◽  
Seismicity Rates ◽  
Splay Faults ◽  
Kodiak Islands

The Kodiak Islands lie near the southern terminus of the 1964 Great Alaska earthquake rupture area and within the Kodiak subduction zone segment. Both local and trans-Pacific tsunamis were generated during this devastating megathrust event, but the local tsunami source region and the causative faults are poorly understood. We provide an updated view of the tsunami and earthquake hazard for the Kodiak Islands region through tsunami modelling and geophysical data analysis. Through seismic and bathymetric data, we characterize a regionally extensive sea floor lineament related to the Kodiak shelf fault zone, with focused uplift along a 50-km long portion of the newly named Ugak fault as the most likely source of the local Kodiak Islands tsunami in 1964. We present evidence of Holocene motion along the Albatross Banks fault zone, but suggest that this fault did not produce a tsunami in 1964. We relate major structural boundaries to active forearc splay faults, where tectonic uplift is collocated with gravity lineations. Differences in interseismic locking, seismicity-rates, and potential field signatures argue for different stress conditions at depth near presumed segment boundaries. We find that the Kodiak segment boundaries have a clear geophysical expression and are linked to upper plate structure and splay faulting. The tsunamigenic fault hazard is higher for the Kodiak shelf fault zone when compared to the nearby Albatross Banks fault zone, suggesting short travel paths and little tsunami warning time for nearby communities.

OBSERVATION AND SIMULATION OF TSUNAMIS INDUCED BY THE 2003 TOKACHI-OKI EARTHQUAKE (M 8.0)

2015 ◽  
Vol 2 (3) ◽  
Author(s):  
Tatsuo Ohmachi ◽  
Shusaku Inoue ◽  
Tetsuji Imai
Keyword(s):  
Rayleigh Wave ◽  
Water Pressure ◽  
Near Field ◽  
Source Region ◽  
Tsunami Source ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Tsunami Simulation ◽  
Sea Bed ◽  
Band Pass

The 2003 Tokachi-oki earthquake (MJ 8.0) occurred off the southeastern coast of Tokachi, Japan, and generated a large tsunami which arrived at Tokachi Harbor at 04:56 with a wave height of 4.3 m. Japan Marine Science and Technology Center (JAMSTEC) recovered records of water pressure and sea-bed acceleration at the bottom of the tsunami source region. These records are first introduced with some findings from Fourier analysis and band-pass filter analysis. Water pressure disturbance lasted for over 30 minutes and the duration was longer than those of accelerations. Predominant periods of the pressure looked like those excited by Rayleigh waves. Next, numerical simulation was conducted using the dynamic tsunami simulation technique able to represent generation and propagation of Rayleigh wave and tsunami, with a satisfactory result showing validity and usefulness of this technique. Keywords: Earthquake, Rayleigh wave, tsunami, near-field

scholarly journals Statistical behaviours of earthquake occurrences in the Central Anatolian Region of Turkey: region-time-magnitude analyses

Baltica ◽  
2021 ◽  
pp. 157-173
Author(s):  
Serkan Öztürk
Keyword(s):  
Fault Zone ◽  
Earthquake Hazard ◽  
B Value ◽  
Short Term ◽  
Small Magnitude ◽  
Strong Earthquakes ◽  
Recurrence Times ◽  
Z Value ◽  
Spatio Temporal

The main objective of this work is to make detailed region-time-magnitude analyses by describing the statistical behaviours of earthquakes in the Central Anatolian Region of Turkey. In this scope, several seismic and tectonic parameters such as Mcomp, b-value, Dc-value, Z-value, recurrence times and annual probabilities were evaluated. For the analyses, a homogeneous catalogue including 10,146 earthquakes with 1.0 ≤ Md ≤ 5.7 between 30 July 1975 and 29 December 2018 was used and spatio-temporal changes of earthquake behaviours were mapped for the beginning of 2019. Earthquake magnitudes varied from 1.9 to 3.0 on average, and hence Mcomp was considered to be 2.6. The b-value was calculated as 1.26 ± 0.07, and this relatively large value indicates that small-magnitude events are dominant. The Dc-value was computed as 1.31 ± 0.03. This small value means that distances between epicentres approach the diameter of the cluster, and seismic activity is more clustered at smaller scales or in larger regions. The spatio-temporal analyses of recurrence times suggest that the Central Anatolian Region has an intermediate/long-term earthquake hazard in comparison to occurrences of strong earthquakes in the short term. Several anomaly regions of a small b-value and a large Z-value were found in and around the Tuzgölü Fault Zone, Central Anatolian Fault Zone, Salanda fault and Niğde fault at the beginning of 2019. Thus, a combination of the regions with a lower b-value, a higher Z-value and also moderate recurrence times may give significant clues for the future possible earthquakes, and detected regions may be thought to be the most likely areas for strong/large events in the Central Anatolian Region.

Time-dependent Tsunami Source Following the 2018 Anak Krakatau Volcano Eruption Inferred from Nearby Tsunami Recordings

2020 ◽  
Author(s):  
Yifan Zhu ◽  
Chao An ◽  
Teng Wang ◽  
Hua Liu
Keyword(s):  
Source Region ◽  
Time Dependent ◽  
Tsunami Source ◽  
Water Volume ◽  
Generation Process ◽  
Tsunami Generation ◽  
Time Duration ◽  
Initial Water ◽  
Volcano Eruption ◽  
Krakatau Volcano

Abstract The eruption of the Anak Krakatau volcano, Indonesia, on 22 December 2018 induced a destructive tsunami (the Sunda Strait tsunami), which was recorded by four nearby tidal gauges. In this study we invert the tsunami records and recover the tsunami generation process. Two tsunami sources are obtained, a static one of instant initial water elevation and a time-dependent one accounting for the continuous evolution of water height. The time-dependent results are found to reproduce the tsunami recordings more satisfactorily. The complete tsunami generation process lasts approximately 9 min and features a two-stage evolution with similar intensity. Each stage lasts about 3.5 min and elevates a water volume of about 0.15 km 3 . The time, duration and volume of the volcano eruption in general agree with seismic records and geomorphological interpretations. We also test different sizes of the potential source region, which lead to different maximum wave height in the source area, but all the results of time-dependent tsunami sources show the robust feature of two stages of wave generation. Our results imply a time-dependent and complex process of tsunami generation during the volcano eruption.

scholarly journals Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile

2016 ◽  
Vol 17 (11) ◽  
pp. 4802-4813 ◽  
Author(s):  
Jacob Geersen ◽  
Florian Scholz ◽  
Peter Linke ◽  
Mark Schmidt ◽  
Dietrich Lange ◽  
...  
Keyword(s):  
Fault Zone ◽  
Central Chile ◽  
Methane Seepage ◽  
Rupture Area ◽  
Maule Earthquake ◽  
2010 Maule Earthquake
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