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SUMMARY The mechanical heterogeneity of Earth's lithosphere leads to significant amplification of stresses across spatial scales ranging from mineral grains to tectonic plates. These stress amplifications play a key role in mechanical and chemical processes within the rock that affect bulk rock strength. Identifying the most effective causes of stress amplification is critical for understanding processes such as strain localization and fluid transport at scales ranging from microshear zones to tectonic plate boundaries. However, studies quantifying and predicting stress heterogeneities and amplifications are limited. We used numerical modelling of two-phase isotropic viscous systems to explore the factors influencing and controlling stress amplification and the potential magnitude of stress amplification in viscous regimes. We found the most geologically relevant amplification factors to be weak-phase spacing, rheological contrast and loading type. Our results indicate that stress amplification can reach a factor of ∼9 under specific conditions, but most of our experiments suggest amplifications at or below a factor of 2. Pressure differences across the model domains generally do not exceed ∼55 MPa, but some are as high as ∼110 MPa. The stress and pressure amplifications resulting from our analyses are large enough to drive a variety of geologically important processes such as failure and strain localization, as well as transient permeability and fluid migration. 

Abstract. With TikTok emerging as one of the most popular social mediaplatforms, there is significant potential for science communicators tocapitalize on this success and to share their science with a broad, engagedaudience. While videos of chemistry and physics experiments are prominentamong educational science content on TikTok, videos related to thegeosciences are comparatively lacking, as is an analysis of what types ofgeoscience videos perform well on TikTok. To increase the visibility of thegeosciences and geophysics on TikTok and to determine best strategies forgeoscience communication on the app, we created a TikTok account called“Terra Explore” (@TerraExplore). The Terra Explore account is a jointeffort between science communication specialists at UNAVCO, IRIS(Incorporated Research Institutions for Seismology), and OpenTopography. Weproduced 48 educational geoscience videos over a 4-month period betweenOctober 2021 and February 2022. We evaluated the performance of each videobased on its reach, engagement, and average view duration to determine thequalities of a successful video. Our video topics primarily focused onseismology, earthquakes, topography, lidar (light detection and ranging),and GPS (Global Positioning System), in alignment with our organizationalmissions. Over this time period, our videos garnered over 2 million totalviews, and our account gained over 12 000 followers. The videos thatreceived the most views received nearly all (∼ 97 %) oftheir views from the For You page, TikTok's algorithmic recommendation feed. Wefound that short videos (< 30 s) had a high average view duration,but longer videos (> 60 s) had the highest engagement rates.Lecture-style videos that were approximately 60 s in length had moresuccess in both reach and engagement. Our videos that received the highestnumber of views featured content that was related to a recent newsworthyevent (e.g., an earthquake) or that explained location-based geology of arecognizable area. Our results highlight the algorithm-driven nature ofTikTok, which results in a low barrier to entry and success for new sciencecommunication creators.