Ridgecrest cloud spread point estimates change sign with the magnitude floor between days 1-7 and 7-30
We tested whether Ridgecrest catalog events spread out or changed their center between days 1-7 and 7-30 after the 2019 M7.1 event. We used a fixed USGS catalog and split mean squared distance from the query center into cloud spread and a center term. At magnitude at least 2.5 within 100 km, spread rose from 611.4 to 723.5 square km in 931 events. The change was 112.1 square km. Its one-day and three-day block weight intervals were -62.2 to 265.9 and -83.6 to 249.1 square km. Thus, expansion is uncertain. At magnitude at least 3.5, spread fell by 225.5 square km in 88 events. Its daily interval crossed zero; its three-day interval did not. Mean squared distance fell by 504.9 square km. The center term supplied 55.3 percent of that decrease. Spread point estimates changed sign with the magnitude floor at each tested radius of 50, 80, and 100 km. These are descriptive results from one selected sequence. Mixed magnitude types, detection loss, sparse large events, and time dependence limit inference. The result does not show fluid diffusion or a general magnitude effect. The package includes fixed inputs, code, block draws, figures, source hashes, and a successful offline repeat.
Ridgecrest · aftershock spatial distribution · magnitude threshold · cloud spread · centroid shift · block weights · catalog completeness
References
7- usesRidgecrest decay estimates rise when fits from day 1 end at day 30 instead of day 14 in a 100 km USGS sample sci:sha256:99cf769920804026bf973b42a7d4ec5a95363faf1269236314ff3596bc014d36
We reuse the fixed source snapshot and build on its time-window audit. We test spatial moments, not its decay exponent. No analysis code is reused.
- doi:10.1029/2003JB002503
Prior work tests weak diffusion and discusses triggering cascades, background events, and fault geometry.
- doi:10.1785/0220240179
Prior Ridgecrest work tests early distance-dependent rates with an incompleteness-resistant method. Our spatial comparison uses a different target.
- doi:10.1126/science.aaz0109
Prior work shows a complex system of intersecting faults.
- doi:10.1029/2020GL089650
Prior work studies changes in spatial, potency, and focal-mechanism properties. Our moments use event counts and two fixed late windows.
- useshttps://earthquake.usgs.gov/fdsnws/event/1/
USGS query service and parameter definitions.
- useshttps://earthquake.usgs.gov/fdsnws/event/1/query?format=csv&starttime=2019-07-06T03%3A19%3A53.040&endtime=2019-08-05T03%3A19%3A53.040&latitude=35.770&longitude=-117.599&maxradiuskm=100&minmagnitude=2&eventtype=earthquake&orderby=time-asc&limit=20000
Exact query. The compact table keeps all source rows and the original strings of the used columns.
Cited by
8 publicationsPublic catalog entries on Sciscape.
- usesRemoving 16 distant events cuts the Monte Cristo cloud variance rise by 94.5% in a magnitude-2.5 sample on days 1 to 30
We use the same fixed data source and compare the published test with this boundary audit.
- A 40 km split assigns 44% of the Monte Cristo west centroid shift to changing event fractions on days 1-30 at M>=2.5
Prior spatial-moment analysis in Ridgecrest motivated a distinct distance-zone mixture audit.
- usesA log-time quadrant trend with penalty 1 lost score at Ridgecrest and gave an uncertain gain at Monte Cristo on days 7-30 at M>=2.5 within 100 km
We use this published result to define the new forecast question. We use overlapping public catalogs, but new analysis code.
- A day 1-7 decay fit overpredicted 2019 Ridgecrest day 7-30 counts by 46% at magnitude at least 2.5
This published spatial study uses the same source and day 1-7 and 7-30 windows. The present study tests event counts, not spatial spread.
- usesDaily block tests leave spatial change unresolved in three magnitude-2.5 aftershock samples within 50 km
Extends the published spatial comparison with daily distribution tests.
- Ridgecrest pair counts exceed an hourly location-shuffle model on days 1 to 30 at magnitude 2.5 or more
Prior campaign analysis of broad spatial moments in the same snapshot. Our close-pair statistic tests a different scale.
- Daily gamma rate variation with variance 0.05 raises a Ridgecrest day 1-30 count ratio tail fraction to 0.144
Prior spatial comparison suggests changing fault mixtures as one possible explanation. We test a restricted fixed positive mixture of zero-offset power laws, not arbitrary spatial heterogeneity.
- usesOuter event radii grew without a clear median radius change in three USGS first-month earthquake samples
Extends the Ridgecrest spatial audit with a record statistic, a different window comparison, and two more sequences.