{"id":"bf71a8b8-8ac7-4e7c-bc9b-64eeb1780ad0","arxiv_id":"2501.16934","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"A dense seismic network search in the Atacama segment found no tectonic tremor or low-frequency earthquakes over 3.5 years, constraining their possible rate and size in a region known for slow slip.","lead":"Researchers ran a three-and-a-half-year systematic search for tectonic tremor and low-frequency earthquakes beneath northern Chile and found none, after sorting through hundreds of thousands of candidate signals. The result suggests that this segment either hosts no such slow-earthquake signals, or produces them too rarely or too weakly to detect, which matters for understanding how slow slip and earthquakes interact on subduction faults.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The null result hinges on an unquantified sensitivity transfer: reference-region success shows only that the pipeline finds known Cascadia/Nankai tremor and LFEs, not that plausible Chilean events with lower moment rate, longer recurrence, or different waveforms would pass; an end-to-end synthetic…","rationale":"The reader's weakest-assumption identification is correct and is the same load-bearing concern I would flag: the absence conclusion depends on the transferability of the defining features of tremor and LFEs from Cascadia/Nankai to Chile—burst-like clustering, high repeat rates, and waveform recognizability by a deep-learning picker trained elsewhere. My stress-test sharpens this into a specific technical gap: the reference-region success demonstrates detection of known intense activity, but it does not provide an end-to-end detection threshold for Chile. The paper's own Section 4.3 lists the limiting assumptions, and Section 4.1 offers only a noise-and-station-density proxy for sensitivity. This is not an internal inconsistency or a fatal flaw; the authors are transparent about the limitations and appropriately hedge the conclusion as 'either lower moment rate, longer recurrence, or absent.' However, the central claim's scientific value lies in placing quantitative bounds on what could still exist, and those bounds are not directly measured. A synthetic injection experiment—running scaled templates through the full pipeline in Chilean data—would directly measure the detection threshold and resolve whether the null result really rules out plausible tremor/LFE activity. The reader's CONDITIONAL verdict is appropriate, and I do not see a reason to change it: the paper should be accepted with the condition that this sensitivity calibration be made explicit and, ideally, that the derived catalogs and pipeline scripts be released for independent re-analysis.","tokens_in":33273,"tokens_out":3138,"duration_ms":32561,"concrete_test":"Inject synthetic tremor and LFE signals into the Chilean continuous data across the full study period, using Cascadia/Nankai LFE templates and tremor envelopes scaled to a range of moment rates (e.g., 1e10 to 1e13 Nm/s) and recurrence patterns (burst-like, isolated, and families with 10–100 repeats), then run the complete detection, DBScan clustering, template matching, and manual classification workflow exactly as in the paper. If injected events above the claimed threshold are recovered as tremor/LFE, the null result is supported; if not, the sensitivity bound must be revised downward and the absence claim weakened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—no evidence for tremor or LFEs over 3.5 years—requires that any geologically plausible tremor or LFE in the Atacama segment would be detected by the pipeline. That condition is not established. The reference-region demonstrations in Section 3.3 show the workflow recovers known, relatively intense, burst-like, highly repetitive events during active migrations in Cascadia and Nankai; they do not calibrate a minimum detectable moment rate, recurrence rate, or waveform family in Chile. Section 4.1 estimates sensitivity from station density and noise alone, yielding only a rough factor-of-two amplitude advantage over Nankai and no end-to-end validation. Section 4.3 explicitly concedes that isolated tremors are removed by DBScan, that LFE families with fewer than 100 detections are rejected by design, and that events with different signal character could be missed by the deep-learning picker. Because the documented SSEs in the region have moment rates near or below the stated detectability range—the 2014 deep SSE is 6e11 Nm/s versus a claimed threshold of roughly 1e12–1e13 Nm/s—the null result is as consistent with 'events exist but are below or at the sensitivity limit' as with true absence. The paper hedges appropriately, but the inference about lower moment rate, longer recurrence, or absence is only as strong as this unquantified transferability assumption.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports a systematic 3.5-year search (November 2020 to February 2024) for tectonic tremor and low-frequency earthquakes (LFEs) in the Atacama segment (24–31°S) of the Chilean subduction zone, using up to 193 onshore stations. Tremor is searched with the envelope-correlation method of Wech (2021) followed by DBScan clustering; LFEs are searched with a deep-learning phase picker followed by association, location, template matching, and family clustering. All surviving tremor clusters (562) and LFE template families (581) are manually inspected against three diagnostic criteria (time-of-day signature, number of phase arrivals, recurrence pattern). No candidate satisfies all LFE criteria and no tremor cluster survives verification; the non-tectonic signals that remain are attributed to mine blasting, teleseismic P-wave arrivals, an offshore active-seismic experiment, and an emergent 20-minute seafloor signal of unresolved origin. The identical workflow applied to one-month windows in Cascadia and Nankai recovers abundant tremor and LFE activity with characteristic migration patterns and interface-consistent depths. The authors conclude that tremors and LFEs in Northern Chile are either of lower moment rate than in other regions, have substantially longer recurrence rates, or are absent altogether, potentially because of the cold subduction environment.","tokens_in":33586,"tokens_out":14940,"duration_ms":128722,"significance":"This is a carefully executed, well-hedged null result with genuine value. If correct, the finding that a dense 3.5-year search in a region hosting documented shallow and deep SSEs recovers no tremor or LFE signals constrains the SSE-tremor relationship and the thermal and fluid controls on tremorgenesis, adding to the small set of cases where SSEs may occur without detectable seismic slow-slip signatures. The paper's strengths are real: two orthogonal detection methods with complementary failure modes; complete manual triage of all 562 surviving tremor clusters and 581 LFE template families; explicit positive controls in Cascadia and Nankai that recover known activity with correct migration patterns and interface-consistent depths; an openly inventoried list of the assumptions on which the null result rests (Section 4.3); and a useful reanalysis of the only prior tremor report for the region (Pastén-Araya et al., 2022), whose reprocessed locations are not interface-compatible.","major_comments":[{"comment":"This comment is complete above; please disregard this duplicate field.","section":"Sections 4.1, 4.4; Appendices A1–A2"},{"comment":"This comment is complete above; please disregard this duplicate field.","section":"Abstract and Section 4.4"},{"comment":"This comment is complete above; please disregard this duplicate field.","section":"Section 3.3 and Appendix A2"}],"minor_comments":[{"comment":"The word 'histrograms' should be 'histograms', and the recurrence-panel y-axis units (log interevent time in seconds?) should be stated in the caption.","section":"Figure 9 caption and Section 3.2"},{"comment":"The word 'expierience' should be 'experience'.","section":"Appendix A2"},{"comment":"The sentences 'This suggest that seismic swarms' and 'accompanied by seismic warms' contain typos; they should read 'This suggests...' and '...seismic swarms'.","section":"Section 2.1"},{"comment":"The claim that the detection-rate dynamic range is lower than in Münchmeyer, Giffard-Roisin, et al. (2024) is qualitative; reporting a quantitative metric (for example, percentile ratios of daily counts on days with similar station counts) would improve reproducibility.","section":"Section 3.2"},{"comment":"The availability of the deep-learning LFE model weights and the LFE workflow scripts is not stated; the envelope-correlation code availability is given, but the LFE side is the less standard component and should be documented.","section":"Open Research"},{"comment":"The sentence 'we expect to see deep tremors with moment rates above 10^12 Nm/s to 10^13 Nm/s' should cross-reference the derivation in Section 4.1 and state explicitly that the bound rests on a noise-level comparison rather than on recovered detections.","section":"Section 4.4"}],"recommendation":"major_revision","confidential_remarks":"The paper is well within the scope of JGR: Solid Earth and the authors are appropriately careful in their claims. One editorial note: the LFE detector (Münchmeyer, Giffard-Roisin, et al., 2024), the velocity model (Münchmeyer et al., 2025), and the present manuscript form a tight cluster of same-group citations; I would encourage the editor to ensure that the cross-region validation of the detector is independently verified during review. The most efficient path to publication is to request the end-to-end sensitivity (injection) test and an abstract rebalancing, as detailed in the major comments."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Jannes,\n\nThis is a careful null result and probably the best we can get on this question without another deployment. The authors ran two orthogonal searches—envelope correlation for tremor, a deep-learning picker for LFEs—over 3.5 years of dense onshore data in the Atacama segment, manually triaged every surviving cluster, and found nothing that survives as tectonic tremor or LFE. They also re-examined the one published tremor report for the region (Pastén-Araya et al., 2022) with their 3D velocity model and make a decent case that those detections locate too deep or too scattered to be interface tremor. That reappraisal alone is a useful piece of work.\n\nThe paper earns credit for being explicit about its assumptions. Section 4.3 says in plain language that isolated tremors are removed by DBScan, that LFE families with fewer than 100 detections are rejected by design, and that a deep-learning picker trained elsewhere could miss region-specific waveforms. The sensitivity comparison to Nankai and Cascadia is honest: Chile has better station density than Cascadia, comparable noise, and about a factor of two worse noise than Nankai at 4–8 Hz. The inference that anything 'typical' would be detected is reasonable, not hand-waving.\n\nThe soft spots are real but mostly inherited from the problem. The stress-test concern is fair: the reference-region validations recover known, intense, bursty tremor during active migrations; they do not calibrate the minimum detectable moment rate or recurrence for Chile. The paper's own numbers show the documented SSEs in the area (6e11 Nm/s for the 2014 deep event) sit near or below the stated sensitivity range (1e12–1e13 Nm/s), so the null result is just as consistent with 'below the floor' as with 'absent.' The authors actually acknowledge this in Section 4.4; the problem is that they do not turn it into a quantitative detectability envelope. An end-to-end synthetic test—inject synthetic tremor/LFE-like sources at plausible depths, moment rates, and recurrence patterns into the actual noise—would have told the reader exactly what is excluded. That is the single biggest gap. The second gap is that the candidate catalogs, template families, and scripts are not released, which matters a lot for a negative result the field will want to re-check.\n\nWho is this for? Anyone working on slow earthquake scaling, tremor generation, or the Chile megathrust. It deserves a serious referee: it is important, the methods are standard but carefully applied, and the conclusion is appropriately hedged. I would take it with a request for synthetic sensitivity tests and data deposition rather than a desk reject.\n\nRecommendation: send it out; ask for injections and code.","headline":"A careful, well-hedged null result for tremor/LFEs in northern Chile; the main gap is the lack of synthetic sensitivity tests, but the paper is worth reviewing and publishing after revisions.","tokens_in":34137,"tokens_out":2353,"would_cite":true,"duration_ms":22517,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"After 3.5 years of continuous seismic monitoring with two independent detection methods and manual verification, the Atacama segment of the Chilean subduction zone shows no evidence of tectonic tremor or low-frequency earthquakes, placing…","keywords":["tectonic tremor","low-frequency earthquakes","Atacama seismic gap","slow slip events","envelope correlation","deep learning seismology","subduction zone","null detection"],"falsifier":"A single well-located repeating LFE family (at least 100 template matches, P and S arrivals, burst-like recurrence, no daytime-only pattern) at 30–40 km depth on the plate interface anywhere in 24°S–31°S, or a coherent envelope-correlation tremor burst located on the interface during the next deep SSE cycle, would directly falsify the absence claim.","tokens_in":33079,"feed_emoji":"🔍","tokens_out":10207,"duration_ms":84382,"temperature":0.7,"pith_summary":"This paper is a systematic attempt to find tectonic tremor and low-frequency earthquakes in the Atacama segment of the Chilean subduction zone, where slow slip events are known to occur but no such seismic companions have ever been confirmed. Over 3.5 years of dense seismic recordings, the authors ran two independent searches — envelope correlation for tremor and a deep learning picker for low-frequency earthquakes — and then filtered every candidate through clustering, matched filtering, and manual waveform inspection. After all that, no candidate remained that could be a real tremor or LFE. The result matters because it sets concrete upper bounds on how large or how frequent such signals would have to be to escape detection, and it sharpens the question of whether some subduction zones produce slow slip without the usual seismic chatter.","feed_headline":"Atacama search finds no tremor or low-frequency quakes in 3.5 years","feed_subtitle":"Two independent detectors and manual checks turned up nothing, tightening bounds on hidden slow-quake signals.","key_machinery":"The argument is carried by two independent detection pipelines. For tremor, the envelope-correlation method of Wech (2021) cross-correlates smoothed 1–8 Hz envelopes across stations in 5-minute windows, locates coherent sources by grid search, and keeps only DBScan clusters of at least five detections to exploit tremor's burst-like recurrence. For LFEs, a deep-learning phase picker trained on Cascadia, Nankai, Guerrero and the San Andreas fault produces P/S picks that are associated and located, then template matching groups repeated waveforms into families that must exceed 100 detections. The final arbiter is manual inspection of each surviving family against three criteria: no anthropogenic time-of-day pattern, two clear phase arrivals, and burst-like (not bimodal or Poissonian) recurrence. Running identical pipelines on Cascadia and Nankai is the control that shows the methods can find tremor and LFEs where they are known to exist.","core_discovery":"The central claim is that the Atacama segment, despite hosting shallow and deep slow slip events, shows no detectable tectonic tremor or LFE activity during November 2020 to February 2024. Roughly 430,000 envelope-correlation detections and 18,640 deep-learning LFE candidates were winnowed by DBScan clustering, template matching, and three diagnostic manual criteria (time-of-day, phase arrivals, recurrence pattern); every surviving family was either an earthquake, mine blast, airgun shot, teleseismic arrival, or an unexplained shallow seafloor signal. The same workflow run on short windows in Cascadia and Nankai recovered known tremors and LFEs with their characteristic migration patterns, so the authors argue the null result is not a methodological failure. They therefore conclude that tremors and LFEs in northern Chile either have moment rates lower than about $10^{12}$–$10^{13}$ Nm/s, recur on timescales longer than the 3.5-year window, behave differently in waveform or clustering than those in Cascadia or Nankai, or are entirely absent — with cold subduction and limited fluid delivery as a plausible cause.","pith_inferences":["A natural extension implied by the thermal hypothesis is that running the identical workflow on a warmer segment of the Chilean margin should recover tremors and LFEs if temperature controls tremor genesis; a null result there would weaken that explanation.","The unexplained 20-minute seafloor signal near 27.5°S resembles a turbidity current; correlating its occurrence with river discharge, sediment supply, or seafloor imagery would identify the source and remove one of the few surviving non-tectonic candidates.","Because the study window sits between the 2020 and roughly 2025 deep SSE recurrences, an instrumented continuation through the next SSE cycle could distinguish 'absent' from 'not during this window,' which the current data cannot do.","If tremor and LFE moment rate scales with SSE slip rate as proposed generally, the low moment rates of Atacama SSEs ($6\\times10^{11}$–$3\\times10^{12}$ Nm/s) predict signals near or below the network's detection floor; borehole or array data could test this scaling by lowering the noise floor."],"forward_implications":["If the null result holds, Atacama becomes a documented case of a subduction zone with slow slip events but no detectable tremor or LFE activity, so slow slip there is not always accompanied by these seismic signals.","The same workflows recovered tremor and LFE in Cascadia and Nankai, validating the sensitivity of the methods and making a methodological failure an unlikely explanation.","The detection threshold implies that any undetected deep tremor or LFE in the region must have moment rate below roughly $10^{12}$–$10^{13}$ Nm/s, or recur less often than once in 3.5 years, or lack the burst and repeat structure assumed.","The previous single-day tremor report around the Copiapó ridge is reinterpreted as likely non-tectonic, since reprocessing places the sources too deep or off-interface and 3.5 years of denser data show nothing similar.","The results provide an observational constraint for models of tremor generation, fluid availability, and temperature-dependent slow slip, particularly the idea that cold subduction suppresses tremor."],"supporting_citations":[{"why":"Supplies the envelope-correlation tremor detector and the DBScan clustering step that removes isolated detections.","marker":"Wech, 2021"},{"why":"Provides the deep-learning LFE phase picker and the evidence that it transfers across regions.","marker":"Münchmeyer, Giffard-Roisin, et al., 2024"},{"why":"Defines the LFE characteristics (repetitive families, low-frequency spectra) used as detection and classification criteria.","marker":"Bostock et al., 2015"},{"why":"Documents the 2014 deep SSE in Atacama, establishing the target zone and its slow-slip moment rate.","marker":"Klein et al., 2018"},{"why":"Confirms the roughly 5-year SSE recurrence that places the study window between known deep SSEs.","marker":"Klein et al., 2022"},{"why":"Reports the only prior tremor detections in the region; the paper reprocesses them and finds their locations incompatible with interface tremor.","marker":"Pastén-Araya et al., 2022"},{"why":"Establishes the high repeat counts and family structure of LFEs that justify the at-least-100-detection template requirement.","marker":"Shelly, 2017"},{"why":"Supplies the Nankai LFE reference catalog used to validate the LFE detection workflow.","marker":"Kato & Nakagawa, 2020"},{"why":"Provides the slow-earthquake moment-rate scaling used to estimate the size of tremors the network could detect.","marker":"Ide & Beroza, 2023"},{"why":"Supplies the 3D velocity model and dense earthquake catalog used for locating candidates and excluding earthquakes.","marker":"Münchmeyer et al., 2025"}],"fun_headline_variants":["Atacama yields zero tremor or LFE detections in 3.5 years","3.5 years of seismic search: no tremor, no low-frequency quakes","Cold subduction may explain missing tremor in northern Chile","After deep learning and manual checks, Atacama shows no tremor","Tremor hunt in Atacama comes up empty despite slow-slip events"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The entire null result rests on the assumption that any tremor or LFE in northern Chile would resemble the ones in Cascadia and Nankai: strong enough to rise above noise on the onshore network, burst-like enough to survive clustering, repeating at least 100 times per family, and with waveforms a cross-region deep-learning picker would recognize.","fun_headline_variants_meta":{"raw":{"variants":["Atacama yields zero tremor or LFE detections in 3.5 years","3.5 years of seismic search: no tremor, no low-frequency quakes","Cold subduction may explain missing tremor in northern Chile","After deep learning and manual checks, Atacama shows no tremor","Tremor hunt in Atacama comes up empty despite slow-slip events"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000282,"raw_usage":{"total_tokens":1748,"prompt_tokens":1105,"completion_tokens":643,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":721,"completion_tokens_details":{"reasoning_tokens":545}},"tokens_in":721,"tokens_out":643,"duration_ms":4976,"temperature":1.0,"reasoning_tokens":545,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T05:30:33.858533+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A single well-located repeating LFE family (at least 100 template matches, P and S arrivals, burst-like recurrence, no daytime-only pattern) at 30–40 km depth on the plate interface anywhere in 24°S–31°S, or a coherent envelope-correlation tremor burst located on the interface during the next deep SSE cycle, would directly falsify the absence claim.","supporting_citations":[{"cited_title":"APACrefauthors \\ 2021","cited_arxiv_id":null,"evidence_quote":"Supplies the envelope-correlation tremor detector and the DBScan clustering step that removes isolated detections."},{"cited_title":", Thomas, A M","cited_arxiv_id":null,"evidence_quote":"Defines the LFE characteristics (repetitive families, low-frequency spectra) used as detection and classification criteria."},{"cited_title":", Duputel, Z","cited_arxiv_id":null,"evidence_quote":"Documents the 2014 deep SSE in Atacama, establishing the target zone and its slow-slip moment rate."},{"cited_title":", Potin, B","cited_arxiv_id":null,"evidence_quote":"Reports the only prior tremor detections in the region; the paper reprocesses them and finds their locations incompatible with interface tremor."},{"cited_title":"APACrefauthors \\ 2017","cited_arxiv_id":null,"evidence_quote":"Establishes the high repeat counts and family structure of LFEs that justify the at-least-100-detection template requirement."},{"cited_title":"\\ Nakagawa, S","cited_arxiv_id":null,"evidence_quote":"Supplies the Nankai LFE reference catalog used to validate the LFE detection workflow."}],"review_version":1}