Description: In May of 2019 the US American research vessel Marcus G. Langseth shot seismic profile p01 across the Emperor Seamounts in the northwest Pacific Ocean. Shots were recorded on 27 ocean-bottom-seismometers (OBS) of the US American Pool and GEOMAR Helmholtz Centre for Ocean Research Kiel. Seismic data in SEGY format of the GEOMAR OBS are here available from PANGAEA Datacenter. Please note that the data have a time offset of 1 sec and a reduction velocity of 8 km/s. The SEGY data from the US American OBS are available at the Incorporated Research Institution for Seismology (IRIS) under the network code ZU. The seismic survey was funded by the US American National Science Foundation (Awards OCE17-37243, OCE17-37245).

Description: We present the results of our analysis of the seismogenic and tsunamigenic structure of the Alboran Basin (westernmost Mediterranean). In particular, we upload two different types of files: 1) the 3D model of a fault plane and 2) the results of the numerical tsunami simulations for the 4 main faults in the area, the Alboran Ridge Fault System (ARFS), the Carboneras Fault System (CFS), the Yusuf Fault System (YFS) and the Al-Idrissi Fault System (AIFS). In order to perform a first approach to the tsunamigenic potential of these active structures, different models have been run with different input parameters (see metadata description). The fault plane has been obtained based on the analysis of active seismic data collected in the area, and the tsunami simulations have been obtained using the HySEA code. For details about the method, and the discussion of the different parameters used in the models, please see the related article "A first appraisal of the seismogenic and tsunamigenic potential of the largest fault systems of the westernmost Mediterranean" (Gómez de la Peña et al., Marine Geology, 2022).

Description: The intraplate Hawaiian-Emperor Seamount Chain has long been considered a hotspot track generated by the motion of the Pacific plate over a deep mantle plume, and an ideal feature therefore for studies of volcanic structure, magma supply, plume-crust interaction, flexural loading, and upper mantle rheology. Despite their importance as a major component of the chain, the Emperor Seamounts have been relatively little studied. In this paper, we present the results of an active-source wide-angle reflection and refraction experiment conducted along an ocean-bottom-seismograph (OBS) line oriented perpendicular to the seamount chain, crossing Jimmu guyot. The tomographic P wave velocity model, using ∼20,000 travel times from 26 OBSs, suggests that there is a high-velocity (〉6.0 km/s) intrusive core within the edifice, and the extrusive-to-intrusive ratio is estimated to be ∼2.5, indicating that Jimmu was built mainly by extrusive processes. The total volume for magmatic material above the top of the oceanic crust is ∼5.3 × 104 km3, and the related volume flux is ∼0.96 m3/s during the formation of Jimmu. Under volcanic loading, the ∼5.3-km-thick oceanic crust is depressed by ∼3.8 km over a broad region. Using the standard relationships between Vp and density, the velocity model is verified by gravity modeling, and plate flexure modeling indicates an effective elastic thickness (Te) of ∼14 km. Finally, we find no evidence for large-scale magmatic underplating beneath the pre-existing crust.

Description: Highlights • We identify the largest active fault systems of the Alboran Basin. • Characterization of faults is key for accurate tsunamigenic potential estimations. • Alboran largest fault systems may generate Mw 〉 7 earthquakes. • These earthquakes have the potential to generate significant tsunami waves approaching the coast. Abstract The westernmost Mediterranean hosts part of the plate boundary between the European and African tectonic plates. Based on the scattered instrumental seismicity, this boundary has been traditionally interpreted as a wide zone of diffuse deformation. However, recent seismic images and seafloor mapping studies support that most of the plate convergence may be accommodated in a few tectonic structures, rather than in a broad region. Historical earthquakes with magnitudes Mw 〉 6 and historical tsunamis support that the low-to-moderate instrumental seismicity might also have led to underestimation of the seismogenic and tsunamigenic potential of the area. We evaluate the largest active faults of the westernmost Mediterranean: the reverse Alboran Ridge, and the strike-slip Carboneras, Yusuf and Al-Idrissi fault systems. For the first time, we use a dense grid of modern seismic data to characterize the entire dimensions of the main fault systems, accurately describe the geometry of these structures and estimate their seismic source parameters. Tsunami scenarios have been tested based on 3D-surfaces and seismic source parameters, using both uniform and heterogeneous slip distributions. The comparison of our results with previous studies, based on limited information on the fault geometry and kinematics, indicates that accurate fault geometries and heterogeneous slip distributions are needed to properly assess the seismic and tsunamigenic potential in this area. Based on fault scaling relations, the four fault systems have a large seismogenic potential, being able to generate earthquakes with Mw 〉 7. The reverse Alboran Ridge Fault System has the largest tsunamigenic potential, being able to generate a tsunami wave amplitude greater than 3 m in front of the coasts of Southern Spain and Northern Africa.