The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP$^3$ to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3--5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5-6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure - as was determined through an extensive, almost two years long campaign - was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign -- described in detail in this paper -- the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole finally reached a depth of 40 cm, bringing the mole body 1--2 cm below the surface. The penetration record of the mole and its thermal sensors were used to measure thermal and mechanical soil parameters such as the thermal conductivity and the penetration resistance of the duricrust and its cohesion. The hammerings of the mole were recorded by the seismometer SEIS and the signals could be used to derive a P-wave velocity and a S-wave velocity and elastic moduli representative of the topmost tens of cm of the regolith. The combined data were used to derive a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick unconsolidated layer of sand mixed with dust and above another 10 cm of unconsolidated sand. Underneath the latter, a layer more resistant to penetration and possibly consisting of debris from a small impact crater is inferred.

Summary Ocean Bottom Seismic (OBS) data that are adequately sampled on the source side allow for up/down wavefield decomposition and removal of all surface-related multiples by means of deconvolution of the downgoing wavefield from the upgoing wavefield. However, conventional sequential acquisition of an adequately sampled shot grid can be costly. Instead, simultaneous source acquisition provides a means to both achieve a productivity increase over conventionally acquired data while also enabling the acquisition of a better sampled shot grid. In this paper we present the results from the first 3D triple-source simultaneous source OBS survey acquired using the principles of signal apparition. We demonstrate that the decoded data allows for a simple bespoke OBS processing workflow to be used resulting in high quality multiple-free images.

The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3–5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5-6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure as was determined through an extensive, almost two years long campaign was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign – described in detail in this paper – the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole finally reached a depth of 40 cm, bringing the mole body 1–2 cm below the surface. It reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the hull. The penetration record of the mole and its thermal sensors were used to measure thermal and mechanical soil parameters such as the penetration resistance of the duricrust of 0.5 1.2 MPa and a penetration resistance of a deeper layer (> 30 cm depth) of 5.3 MPa. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 4 25 kPa depending on the internal friction angle of the duricrust. Pushing the scoop with its blade into the surface and chopping off a piece of duricrust provided another estimate of the cohesion of 5.8 kPa. The hammerings of the mole were recorded by the seismometer SEIS and the signals could be used to derive a P-wave velocity of 114 −19 m/s and a S-wave velocity of 60 +10 −7 m/s (Brinkman et al., 2021) representative of the topmost tens of cm of the regolith. Together with a density of 1211 −113 kg/m 3 (Grott et al., 2021) provided by a thermal conductivity and diffusivity measurement using the mole thermal sensors, the J. Grygorczuk, L. Wisniewski Astronika Sp. z o.o., ul. Bartycka 18, 00-716 Warszawa, Poland F. Andersson, N. Brinkman, P. Edme, D. Giardini, J. Robertsson, C. Schmelzbach, D. Sollberger Institute of Geophysics, Department of Earth Sciences, ETH Zürich, CH-8092 Zürich, Switzerland V. Ansan Laboratoire de Planétologie et Géodynamique de Nantes, Université de Nantes, 44322 Nantes, France P. Delage École nationale des ponts et chaussées, Laboratoire Navier, Paris, France C. Vrettos Department of Civil Engineering, University of Kaiserslautern, Kaiserslautern, Germany P. Lognonné Institut du Physique du Globe Paris, Paris, France O. Krömer Astrium, Bremen, Germany

Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles. The crust beneath the InSight lander on Mars is altered or fractured to 8–11 km depth and may bear volatiles, according to an analysis of seismic noise and wave scattering recorded by InSight’s seismometer.

In November 2018, the InSight lander successfully touched down in the Elysium Planitia plain on Mars. Since then, two scientific instruments were deployed directly onto the surface of Mars: (1) SEIS, a package consisting of two three component seismic sensors and (2) HP3, the heat flow and physical properties package. HP3 includes a self-hammering penetrator (mole) that hammers itself into the subsurface of Mars to a maximum depth of five meters. The mole hammering generates seismic signals that are recorded by SEIS and can be used to image the shallow subsurface just below the landing site. Even though not included in the level-one mission’s objectives, this opportunistic seismic experiment is, to the best of our knowledge, the first active seismic experiment ever conducted on a different planet. Here, we discuss the most important aspects of the implementations of this opportunistic experiment. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Start Time: 3:30 PM Location: 301B Presentation Type: Oral

Summary Signal apparition using triple source in simultaneous mode has been successfully tested in a field trial at the Grane field in the Norwegian North Sea. When used in a repeat setting, spanning eight months of field history, results show that apparition-enabled simultaneous source data acquired in triple source mode is operationally viable, and that subsequent processing provides data suitable for time-lapse analysis. Comparison with standard PRM production data supports these findings.

Summary We present results from a triple-source signal apparition-style field test carried out over a PRM array in the North Sea during the summer of 2017. In addition to the triple-source line, two reference lines were acquired firing the central source only. Assessing the quality of acoustic and elastic P/Z combination confirms high fidelity data quality throughout the bandwidth of the data. Comparing prestack migrated images of elastic P/Z combination against Amundsen demultiple images shows that multiples are a significant challenge in the area and that removing all surface related multiples as done in the Amundsen demultiple method is critical for unambiguous interpretation. Amundsen demultiple requires the deconvolution of the downgoing wavefield from the upgoing wavefield. Thus, the process relies on excellent data fidelity in separated wavefield constituents. We find that comparisons of reference line on reference line display a similar level of residual as the reference line compared to the isolated source result corresponding to the same source location. The reference line compared to the decoded source result corresponding to the other offset source locations display a larger residual. Our results thus confirm that triple-source signal apparition-style acquisition enables highly productive acquisition of seismic data without compromising on data quality.

Seabed seismic data have proven critical for addressing long-standing challenges in seismic imaging both for exploration and especially optimizing reservoir development and management, including broadband data acquisition, full azimuth acquisition, gas clouds or removal of multiples to name a few. Historically, OBS acquisition has been expensive and an increased focus on receiver efficiency and source efficiency is essential to bring the cost down. The Marine Autonomous Seismic System (MASS) is a miniaturized long-battery life 4-component node designed for efficient OBS acquisition (Steen-Hansen, 2017). The compact size allows for handling large numbers of receivers during operations in an automated manner. With such significant advances on the receiver side, a step change is needed for source side technology where little has happened since the advent of flip/flop acquisition in the early 1980’s.

Summary Signal apparition offers a new perspective on sampling of seismic data. It can be used as a fundamentally different approach to decode data acquired in a simultaneous source mode. Results from the first field test using seabed recordings in the North Sea are presented and we find that by using signal apparition principles it is possible to obtain simultaneous source separation results with very low separation errors resulting in 4D-grade separated seismic data. Our finding will have significant implications on acquisition cost and efficiency gains.

Summary In wavefield signal apparition, acquisition with periodic variations in source activation parameters shifts all or part of a signal cone out to, e.g., the Nyquist wavenumber, enabling perfect separation of simultaneous-source (sim-source) data in a diamond-shaped region below a certain temporal frequency. Cyclic convolution in the spatial frequency domain can be exploited to separate data with known non-periodic encoding functions. Such a separation comprises a least-squares reconstruction in the frequency-wavenumber (fk) domain. By applying the reconstruction in the S-transform domain and using an exact expression for NMO stretch, it is possible to perform anti-aliased source separation in conjunction with an invertible NMO or when pre-processing renders the encoding time and space-variant.

Summary Signal apparition offers a fundamentally new perspective on simultaneous source separation. Whereas the method exactly separates the signal from interfering sources in diamond-shaped regions of the f-k space, signal from simultaneous source still overlap outside these regions. We present a method based on using local phase functions and the analytic part of the blended data to reconstruct the separated data throughout the full data bandwidth.

Simultaneous source acquisition promises great efficiency gains but its suitability for reservoir monitoring applications remains contested. By utilizing an approach for simultaneous source acquisition, based on a novel view of seismic data sampling principles that is completely different to existing methods, we demonstrate that 4D-grade seismic data can be obtained from an OBS field data set acquired in the North Sea. Main drivers for developing this new simultaneous source technique are to create significant cost savings and increased flexibility in data acquisition for reservoir monitoring applications.

Shot isolation enabled full-fold, multi-source acquisition is achieved by applying the novel technology of signal apparition to the encoding and decoding of fully superimposed shot records from non-distance separated sources. The introduction of periodically varying shot-to-shot modulation functions for encoding injects energy at predetermined positions within distinct wavenumber ranges, which then enables a deterministic decoding of individual shots in data processing. We demonstrate the method for single vessel operations, first on a dual source configuration for seabed acquisition, extracted from the SEG Advanced Modeling Program (SEAM) Phase I dataset, and then extend the methodology to triple-sources through the use of an emulated marine real data example from the North Sea. With shot isolation enabled multi-source acquisition being successfully applied in a marine and seabed seismic context, scope for significant productivity gains is created. Compared to established acquisition techniques, gains arise from the ability to acquire full-fold data in a shorter time frame without compromising the subsurface bin size. For marine seismic acquisition, this also implies that the number of towed streamers can be reduced, giving leeway to additional strategic considerations on subjects such as capital expenditures and the optimization of vessel deployment plans.

Summary In conventional seismic surveys, there is a waiting time between sequentially fired shots. This time is determined such that the deepest reflection of interest is recorded before the following source is fired. In a survey with simultaneous or blended sources, the waiting time between the firing of shots is not dependent on the deepest reflection of interest, it is usually much shorter and/or can have random time delays. Thus, the wavefields due to independent sources are overlapped in the records. The blended data exhibit strong discontinuities in the source direction, in contrast to the coherency expected from seismic measurements. A strategy for deblending could then be to suppress these discontinuities. In this paper, we propose to do this by designing an energy functional that uses a combination of individual functionals that penalize deviations from local plane waves in the reconstructed (deblended) data, as well as a least squares term that penalizes discrepancies between the deblended and the measured data. In this way, we derive a set of coupled nonlinear partial differential equations that we use for the deblending procedure.