An Investigation of Fin and Blue Whales in the NE Pacific Ocean using Data from Cascadia Initiative Ocean Bottom Seismometers

2014 ◽  
Author(s):  
William S. Wilcock ◽  
David K. Mellinger
Keyword(s):  
Pacific Ocean ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometers ◽  
Using Data ◽  
Ne Pacific ◽  
Blue Whales

scholarly journals The GROSMarin experiment: three dimensional crustal structure of the North Ligurian margin from refraction tomography and preliminary analysis of microseismic measurements

2011 ◽  
Vol 182 (4) ◽  
pp. 305-321 ◽  
Author(s):  
Jean-Xavier Dessa ◽  
Soazig Simon ◽  
Marjorie Lelievre ◽  
Marie-Odile Beslier ◽  
Anne Deschamps ◽  
...  
Keyword(s):  
Preliminary Analysis ◽  
Deep Structure ◽  
Three Dimensional ◽  
Ocean Bottom ◽  
Deep Basin ◽  
The North ◽  
Refraction Tomography ◽  
Refraction Seismic ◽  
Ocean Bottom Seismometers ◽  
Using Data

Abstract The deep structure of the North Ligurian margin and its contiguous Ligurian basin as well as the seismicity recorded in these zones are neither well understood nor precisely constrained. In order to better address these questions, there is a need for offshore instrumenting, which was realised for a duration of nearly 6 months during the GROSMarin (Grand Réseau d’Observation Sous-Marin) experiment. An array of 21 ocean bottom seismometers was deployed over the most active area of the margin and was complemented on land by mobile seismological stations that densified existing permanent networks. We also realised the acquisition of deep refraction seismic shots at sea in order to get a 3D distribution of velocities along the margin through travel time tomography. We present here a preliminary analysis of the seismicity recorded during this experiment and a tomographic model of the margin structures obtained using data from the offshore network only. Our results support the existence of a high velocity zone at the base of a domain interpreted as transitional between continental and oceanic ones, on the northern part of the deep basin. A very similar pattern is observed across the neighbouring margin of the Gulf of Lions and is most likely related to serpentinisation of the underlying mantle during late rifting and continental break-up. North of this transition zone, we observe the basinward crustal thinning of the continental crust beneath the margin that seemingly narrows eastward. To the south, our results hint at transition to the oceanic domain. In contrast, our velocity distribution does not reveal a transition along strike between transitional and oceanic domains, as previous works suggest. Some microseismic activity was recorded throughout the duration of the experiment, on land and at sea. The number of detected events and precision of location were both improved by our considering French and Italian permanent networks. The detection capabilities of our dense network still need to be fully exploited.

scholarly journals A method for tracking blue whales (Balaenoptera musculus) with a widely spaced network of ocean bottom seismometers

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260273
Author(s):  
William S. D. Wilcock ◽  
Rose S. Hilmo
Keyword(s):  
Pacific Northwest ◽  
Marine Mammals ◽  
Likelihood Function ◽  
Double Difference ◽  
Ocean Bottom ◽  
Large Network ◽  
Ocean Bottom Seismometer ◽  
Balaenoptera Musculus ◽  
Ocean Bottom Seismometers ◽  
Blue Whales

Passive acoustic monitoring is an important tool for studying marine mammals. Ocean bottom seismometer networks provide data sets of opportunity for studying blue whales (Balaenoptera musculus) which vocalize extensively at seismic frequencies. We describe methods to localize calls and obtain tracks using the B call of northeast Pacific blue whale recorded by a large network of widely spaced ocean bottom seismometers off the coast of the Pacific Northwest. The first harmonic of the B call at ~15 Hz is detected using spectrogram cross-correlation. The seasonality of calls, inferred from a dataset of calls identified by an analyst, is used to estimate the probability that detections are true positives as a function of the strength of the detection. Because the spacing of seismometers reaches 70 km, faint detections with a significant probability of being false positives must be considered in multi-station localizations. Calls are located by maximizing a likelihood function which considers each strong detection in turn as the earliest arrival time and seeks to fit the times of detections that follow within a feasible time and distance window. An alternative procedure seeks solutions based on the detections that maximize their sum after weighting by detection strength and proximity. Both approaches lead to many spurious solutions that can mix detections from different B calls and include false detections including misidentified A calls. Tracks that are reliable can be obtained iteratively by assigning detections to localizations that are grouped in space and time, and requiring groups of at least 20 locations. Smooth paths are fit to tracks by including constraints that minimize changes in speed and direction while fitting the locations to their uncertainties or applying the double difference relocation method. The reliability of localizations for future experiments might be improved by increasing sampling rates and detecting harmonics of the B call.

scholarly journals On sampling the upper crustal reservoir of the NE Pacific Ocean

Geofluids ◽  
2006 ◽  
Vol 0 (0) ◽  
pp. 060623055813001-??? ◽  
Author(s):  
H. P. JOHNSON ◽  
J. A. BAROSS ◽  
T. A. BJORKLUND
Keyword(s):  
Pacific Ocean ◽  
Ne Pacific

scholarly journals Microearthquake seismicity and focal mechanisms at the Rodriguez Triple Junction in the Indian Ocean using ocean bottom seismometers

2001 ◽  
Vol 106 (B12) ◽  
pp. 30689-30699 ◽  
Author(s):  
Kei Katsumata ◽  
Toshinori Sato ◽  
Junzo Kasahara ◽  
Naoshi Hirata ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
Focal Mechanisms ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometers ◽  
The Indian Ocean
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