Andrea Cecilia Duran

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Duran

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Andrea Cecilia

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0000-0003-4269-930X

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Publications 1 - 9 of 9

Observation of a Core-Diffracted P-Wave From a Farside Impact With Implications for the Lower-Mantle Structure of Mars
Duran, Andrea Cecilia; Khan, Amir; Ceylan, Savas; et al. (2022)
Geophysical Research Letters
We report on the observation of a diffracted P-wave (Pdiff) along the core of Mars from a distant impact that has been recorded by the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission. The identification of Pdiff allows us to sample the P-wave velocity structure of the lower mantle that hitherto could not be constrained because of lack of lower-mantle-traversing P-waves. In addition to Pdiff, we are able to pick PP-, PPP-, and SS-wave arrivals and locate the event to the farside of Mars in the vicinity of Tharsis, in agreement with the imaged location of the impact. This indicates that our joint single-station seismic event-location and structure-inversion scheme is both robust and accurate. Based on inversion of the body-wave arrival time picks made here, we find lower P-wave velocities in the deep mantle relative to predictions based on thermochemically homogeneous models.
Evidence for a liquid silicate layer atop the Martian core
Khan, Amir; Huang, Dongyang; Duran, Andrea Cecilia; et al. (2023)
Nature
Seismic recordings made during the InSight mission suggested that Mars’s liquid core would need to be approximately 27% lighter than pure liquid iron, implying a considerable complement of light elements. Core compositions based on seismic and bulk geophysical constraints, however, require larger quantities of the volatile elements hydrogen, carbon and sulfur than those that were cosmochemically available in the likely building blocks of Mars. Here we show that multiply diffracted P waves along a stratified core–mantle boundary region of Mars in combination with first-principles computations of the thermoelastic properties of liquid iron-rich alloys require the presence of a fully molten silicate layer overlying a smaller, denser liquid core. Inverting differential body wave travel time data with particular sensitivity to the core–mantle boundary region suggests a decreased core radius of 1,675 ± 30 km associated with an increased density of 6.65 ± 0.1 g cm⁻³, relative to previous models, while the thickness and density of the molten silicate layer are 150 ± 15 km and 4.05 ± 0.05 g cm⁻³, respectively. The core properties inferred here reconcile bulk geophysical and cosmochemical requirements, consistent with a core containing 85–91 wt% iron–nickel and 9–15 wt% light elements, chiefly sulfur, carbon, oxygen and hydrogen. The chemical characteristics of a molten silicate layer above the core may be revealed by products of Martian magmatism.
S1222a – The Largest Marsquake Detected by InSight
Kawamura, Taichi; Clinton, John Francis; Zenhäusern, Géraldine; et al. (2023)
Geophysical Research Letters
NASA’s InSight has detected a large magnitude seismic event, labelled S1222a. The event has a moment magnitude of M(Ma)(W)4.7, with 5 times more seismic moment compared to the second largest even. The event is so large that features are clearly observed that were not seen in any previously detected events. In addition to body phases and Rayleigh waves, we also see Love waves, minor arc surface wave overtones, and multi-orbit surface waves. At long periods, the coda event exceeds 10 hours. The event locates close to the North-South dichotomy and outside the tectonically active Cerberus Fossae region. S1222a does not show any evident geological or tectonic features. The event is extremely rich in frequency content, extending from below 1/30 Hz up to 35 Hz. The event was classified as a broadband type event; we also observe coda decay and polarization similar to that of very high frequency type events.
The Far Side of Mars: Two Distant Marsquakes Detected by InSight
Horleston, Anna C.; Clinton, John Francis; Ceylan, Savas; et al. (2022)
The Seismic Record
For over three Earth years the Marsquake Service has been analyzing the data sent back from the Seismic Experiment for Interior Structure—the seismometer placed on the surface of Mars by NASA’s InSight lander. Although by October 2021, the Mars seismic catalog included 951 events, until recently all these events have been assessed as lying within a radius of 100° of InSight. Here we report two distant events that occurred within days of each other, located on the far side of Mars, giving us our first glimpse into Mars’ core shadow zone. The first event, recorded on 25 August 2021 (InSight sol 976), shows clear polarized arrivals that we interpret to be PP and SS phases at low frequencies and locates to Valles Marineris, 146° ± 7° from InSight. The second event, occurring on 18 September 2021 (sol 1000), has significantly more broadband energy with emergent PP and SS arrivals, and a weak phase arriving before PP that we interpret as Pdiff. Considering uncertain pick times and poorly constrained travel times for Pdiff, we estimate this event is at a distance between 107° and 147° from InSight. With magnitudes of MMaw 4.2 and 4.1, respectively, these are the largest seismic events recorded so far on Mars.
Constraints on Midmantle Discontinuities in Mars from Analysis of InSight Seismic Data
Duran, Andrea Cecilia; Khan, Amir; Helffrich, George; et al. (2025)
The Seismic Record
The structure and nature of Earth’s transition zone, which is delineated by the transformation of olivine to its higher-pressure polymorphs, exerts a strong influence on material transfer between upper and lower mantle. Mars, however, because of its relatively large core, is only expected to exhibit the equivalent of Earth’s uppermost transition zone seismic discontinuity. We searched the InSight seismic data for marsquakes and impacts located in an epicentral distance range favorable for detection of seismic phases that have interacted with Mars’s olivine transition (midmantle) discontinuity. Through application of careful data selection criteria and processing schemes, we found 13 events in the distance range in which body waves are expected to refract through the midmantle of Mars. Although triplicated body waves are potentially present in seven events, the distance distribution is insufficient to allow for unambiguous detection of the triplicated waveform pattern associated with the midmantle discontinuity. Comparison of travel times of the observed waveforms with predictions from recent Mars models indicates the possible presence of a midmantle discontinuity located between 987 and 1052 km or 1075 and 1122 km depth, in which the uncertainty comes from our inability to reliably distinguish first from secondary arrivals.
Seismology on Mars: Analysis of Body Waves with Implications for Interior Structure
Duran, Andrea Cecilia (2024)
Mars has been a subject of significant scientific interest for centuries but it remains largely unknown compared to Earth. Despite notable differences in characteristics such as size, the absence of a global magnetic field, tectonic plate activity, and active volcanoes, both planets share a similar interior structure, predominantly composed of a solid silicate rock crust and a mantle encasing an iron core. Yet, without comprehensive seismological data Mars's interior is largely unconstrained. The InSight (Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport) mission, which landed on Mars in late 2018, aimed to understand key aspects of the planet's formation and evolution, including its present level of tectonic activity and impact flux. Equipped with the Seismic Experiments for Interior Structure (SEIS), InSight marked a historic milestone as the first successful mission to collect high-quality seismic data directly from the surface of Mars. SEIS recorded almost continuous data for over more than four Earth years, capturing over 1300 seismic events attributed to both tectonic sources and meteorite impacts. However, SEIS's deployment in Mars's harsh wind and temperature conditions led to inevitable data degradation, with seismic background noise fluctuating throughout the Martian day and various transient signals contaminating the data, challenging the interpretation of seismic data for understanding Mars's interior structure. In line with the primary science goal of the InSight mission, which aims to understand the formation and evolution of terrestrial planets by investigating the interior structure and processes of Mars, the main objective of this thesis is to determine Mars's interior structure through the analysis of seismic data recorded by SEIS. Through data processing, modeling, and inversion techniques, this study aims to achieve the baseline objectives established prior to the mission, including constraining the thickness and structure of the crust, characterizing the composition and structure of the mantle, elucidating the size, composition, and physical state of the core, and investigating the thermal conditions within the planet's interior. Hence, we apply advanced single-station analysis methodologies on SEIS data to identify body waves that propagate through the interior of Mars. These waves offer crucial insights into the planet's internal structure and the characteristics of the layers they encounter. Through iterative application of complementary approaches, we augment the number of detected body-wave phases compared to prior analyses, leading to a substantial gain in information that significantly advances our understanding of Mars's seismic interior structure, from the surface layers to its core. Our findings provide the first constraints on seismic velocities in the deep Martian mantle, revealing deviations from predictions based on thermochemically homogeneous models. Additionally, we detect core-transiting seismic waves from distant events, enabling the construction of the first seismically constrained models for the elastic properties of the Martian core. Furthermore, we find evidence that supports a fully molten silicate layer overlying a smaller, denser liquid core than previously estimated. Moreover, our single-station event-location and structure-inversion methodology proves robust and accurate, as demonstrated by its agreement with the imaged location of an impact event. Lastly, we conduct a detailed analysis of continuous SEIS data to detect Mars's background free oscillations, and evaluate their implications for the planet's internal structure in comparison to results obtained from body waves. Together, this work offers a comprehensive analysis approach to identify body-wave arrivals and background free oscillations in the data recorded by SEIS, contributing to a notable enhancement in information acquisition concerning the interior of Mars. These findings have significantly contributed to a better understanding of Mars's internal structure and composition and prove promising for future planetary missions.
The Global Seismic Moment Rate of Mars After Event S1222a
Knapmeyer, Martin; Stähler, Simon Christian; Plesa, Ana-Catalina; et al. (2023)
Geophysical Research Letters
The seismic activity of a planet can be described by the corner magnitude, events larger than which are extremely unlikely, and the seismic moment rate, the long-term average of annual seismic moment release. Marsquake S1222a proves large enough to be representative of the global activity of Mars and places observational constraints on the moment rate. The magnitude-frequency distribution of relevant Marsquakes indicates a b-value of 1.06. The moment rate is likely between 1.55×1015Nm∕a and 1.97×1018Nm∕a, with a marginal distribution peaking at 4.9×1016Nm∕a. Comparing this with pre-InSight estimations shows that these tended to overestimate the moment rate, and that 30% or more of the tectonic deformation may occur silently, whereas the seismicity is probably restricted to localized centers rather than spread over the entire planet.
Global Crustal Thickness Revealed by Surface Waves Orbiting Mars
Kim, Doyeon; Duran, Andrea Cecilia; Giardini, Domenico; et al. (2023)
Geophysical Research Letters
We report observations of Rayleigh waves that orbit around Mars up to three times following the S1222a marsquake. Averaging these signals, we find the largest amplitude signals at 30 and 85 s central period, propagating with distinctly different group velocities of 2.9 and 3.8 km/s, respectively. The group velocities constraining the average crustal thickness beneath the great circle path rule out the majority of previous crustal models of Mars that have a >200 kg/m(3) density contrast across the equatorial dichotomy between northern lowlands and southern highlands. We find that the thickness of the Martian crust is 42-56 km on average, and thus thicker than the crusts of the Earth and Moon. Considered with the context of thermal evolution models, a thick Martian crust suggests that the crust must contain 50%-70% of the total heat production to explain present-day local melt zones in the interior of Mars.
Searching the InSight Seismic Data for Mars’s Background-Free Oscillations
Duran, Andrea Cecilia; Khan, Amir; Kemper, Johannes Maximilian; et al. (2025)
Seismological Research Letters
Mars’s atmosphere has theoretically been predicted to be strong enough to continuously excite Mars’s background-free oscillations, potentially providing an independent means of verifying radial seismic body-wave models of Mars determined from marsquakes and meteorite impacts recorded during the Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission. To extract the background-free oscillations, we processed and analyzed the continuous seismic data, consisting of 966 Sols (a Sol is equivalent to a Martian day), collected by the Mars InSight mission using both automated and manual deglitching schemes to remove nonseismic disturbances. We then computed 1-Sol-long autocorrelations for the entire data set and stacked these to enhance any normal-mode peaks present in the spectrum. We find that while peaks in the stacked spectrum in the 2–4 mHz frequency band align with predictions based on seismic body-wave models and appear to be consistent across the different processing and stacking methods applied, unambiguous detection of atmosphere-induced free oscillations in the Martian seismic data nevertheless remains difficult. This possibly relates to the limited number of Sols of data that stack coherently and the continued presence of glitch-related signal that affects the seismic data across the normal-mode frequency range (∼1–10 mHz). Improved deglitching schemes may allow for clearer detection and identification in the future.

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Andrea Cecilia Duran

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