Aftershocks Preferentially Occur in Previously Active Areas
The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power-law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in epidemic-type aftershock...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Seismological Society of America
2022-04-01
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| Series: | The Seismic Record |
| Online Access: | https://doi.org/10.1785/0320220005 |
| _version_ | 1797347623490813952 |
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| author | Morgan T. Page Nicholas J. van der Elst |
| author_facet | Morgan T. Page Nicholas J. van der Elst |
| author_sort | Morgan T. Page |
| collection | DOAJ |
| description | The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power-law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in epidemic-type aftershock sequence (ETAS) modeling and is typically assumed to be isotropic, even though individual sequences show more clustered aftershock occurrence. The assumption of spatially isotropic triggering kernels can impact the estimation of ETAS parameters themselves, such as biasing the magnitude-productivity term, alpha, and assigning too much weight to secondary rather than primary (direct) triggering. Here we show that aftershock locations in southern California, at all mainshock–aftershock distances, preferentially occur in the areas of previous seismicity. For a given sequence, the scaling between aftershock rates and the previous seismicity rate is approximately linear. However, the total number of aftershocks observed for a given sequence is independent of background rate. We explain both of these observations within the framework of rate-and-state friction (Dieterich, 1994). |
| first_indexed | 2024-03-08T11:50:28Z |
| format | Article |
| id | doaj.art-7b9bef1d513344f988e68afe6c5757d4 |
| institution | Directory Open Access Journal |
| issn | 2694-4006 |
| language | English |
| last_indexed | 2024-03-08T11:50:28Z |
| publishDate | 2022-04-01 |
| publisher | Seismological Society of America |
| record_format | Article |
| series | The Seismic Record |
| spelling | doaj.art-7b9bef1d513344f988e68afe6c5757d42024-01-24T13:11:45ZengSeismological Society of AmericaThe Seismic Record2694-40062022-04-012210010610.1785/032022000522005Aftershocks Preferentially Occur in Previously Active AreasMorgan T. Page0https://orcid.org/0000-0001-9321-2990Nicholas J. van der Elst1https://orcid.org/0000-0002-3812-1153U.S. Geological Survey, Pasadena, California, U.S.A.U.S. Geological Survey, Pasadena, California, U.S.A.The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power-law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in epidemic-type aftershock sequence (ETAS) modeling and is typically assumed to be isotropic, even though individual sequences show more clustered aftershock occurrence. The assumption of spatially isotropic triggering kernels can impact the estimation of ETAS parameters themselves, such as biasing the magnitude-productivity term, alpha, and assigning too much weight to secondary rather than primary (direct) triggering. Here we show that aftershock locations in southern California, at all mainshock–aftershock distances, preferentially occur in the areas of previous seismicity. For a given sequence, the scaling between aftershock rates and the previous seismicity rate is approximately linear. However, the total number of aftershocks observed for a given sequence is independent of background rate. We explain both of these observations within the framework of rate-and-state friction (Dieterich, 1994).https://doi.org/10.1785/0320220005 |
| spellingShingle | Morgan T. Page Nicholas J. van der Elst Aftershocks Preferentially Occur in Previously Active Areas The Seismic Record |
| title | Aftershocks Preferentially Occur in Previously Active Areas |
| title_full | Aftershocks Preferentially Occur in Previously Active Areas |
| title_fullStr | Aftershocks Preferentially Occur in Previously Active Areas |
| title_full_unstemmed | Aftershocks Preferentially Occur in Previously Active Areas |
| title_short | Aftershocks Preferentially Occur in Previously Active Areas |
| title_sort | aftershocks preferentially occur in previously active areas |
| url | https://doi.org/10.1785/0320220005 |
| work_keys_str_mv | AT morgantpage aftershockspreferentiallyoccurinpreviouslyactiveareas AT nicholasjvanderelst aftershockspreferentiallyoccurinpreviouslyactiveareas |