+VQMCYC’U ETCVGTKPI TGEQTF
CUQDUGTXGFD[*C[CDWUCᲴ+ORNKECVKQPUHQTKVUCIG+ECTWU   2/KEJGN &21 $TKGP  5#DG  0*KTCVCో૕䈱ᵹ䉏
╙1┨䋺䉟䊮䊃䊨䉻䉪䉲䊢䊮╙2┨䋺䉟䊃䉦䊪䈱⴫㕙਄䈱䉪䊧䊷䉺䊷ኒᐲ䈮䈧䈇䈩
╙3┨䋺O’Brien et al.(2006)䈱䊝䊂䊦䈱䉟䊃䉦䊪䈻䈱ㆡ↪
╙5┨䋺࿾㔡േ䈮䈧䈇䈩╙4┨䋺䉟䊃䉦䊪෸䈶䉣䊨䉴䈱䉪䊧䊷䉺䊷ಽᏓ䈮ၮ䈨䈒ᐕઍ䈱⸘▚╙6┨䋺䉟䊃䉦䊪䈱ዊ䈘䈇䉪䊧䊷䉺䊷䈏ዋ䈭䈇䈖䈫䈮䈧䈇䈩╙7┨䋺⚿ᨐ䈫⚿⺰䈱ⷐ⚂Შ+PVTQFWEVKQPǤȈǫȯƱƸᲹ í䂾䉰䉟䉵䋺535 m 㬍 294 m 㬍 209 m
䂾Sဳዊᖺᤊ䈮ዻ䈚䇮࿾⃿ㄭறዊᄤ૕䋨NEO䋩䈱䋱䈧䊶ജቇ⊛ㅴൻ䋺࿾⃿䈮ㄭធㆣㆄ䈜䉎䊶⿠Ḯ䋺䊜䉟䊮䊔䊦䊃䈱ౝ஥䂾 “䊤䊑䊦䊌䉟䊦” ᄤ૕䈫⠨䈋䉌䉏䉎䋨⚂ 2 g/cm3 䇮ⓨ㓗₸䈲⚂40% 䋩25143䉟䊃䉦䊪ǤȈǫȯƱƸᲹ î䂾䊤䉾䉮䉂䈢䈇䈭ᒻ䂾⴫㕙䋺⿠ફ䈏ᄙ䈒䇮 ᄢ䈐䈭ጤ(boulder)䈮ን䉃䊶⴫㕙䈱~80% 䋺"rough terrains"䊶⴫㕙䈱20~% 䋺"smooth terrains"

25143䉟䊃䉦䊪䂾䊜䉟䊮䊔䊦䊃ਛ䈱ઁ䈱ዊᖺᤊ䈫䈱ⴣ⓭䈮䉋䈦䈩䊋䊤䊋䊤䈮⎕უ䈘䉏䈢䉋䉍ᄢ䈐䈭ዊᖺᤊ䈱⎕ 䋨䈫⠨䈋䉌䉏䈩䈇䉎䋩䉟䊃䉦䊪䈱ᐕ㦂䉕⷗Ⓧ䉅䉎䈖䈫䊤䉾䉮Უᄤ૕䈏⎕უ䈘䉏䈩䈎䉌䈖䉏䉁䈪䈱ᤨ㑆䉕᳿䉄䉎䈖䈫ƲƷǑƏƴƠƯǤȈǫȯƷ࠰ᱫǛᙸᆢǋǔƷƔᲹ䂾䈲䉇䈹䈘តᩏᯏ䈮䉋䈦䈩᠟ᓇ䈘䉏䈢䉟䊃䉦䊪⴫㕙䈱䉪䊧䊷䉺䊷䈱ᖱႎ䉕૶䈉䇯㹢 O‘Brien et al.(2006) 䈱䊝䊂䊦䉕૶䈦䈩䇮䉟䊃䉦䊪䈱⴫㕙਄䈱䉪䊧䊷䉺䊷䉕⚥Ⓧ䈜䉎䈱䈮ᔅⷐ䈭ᤨ㑆䉕⸘▚䈖䈱䉇䉍ᣇ䈲䉟䊃䉦䊪䈮䈲਄ᚻ䈒ㆡ↪䈪䈐䈢䇯䈚䈎䈚䇮䉟䊃䉦䊪਄䈱ዊ䈘䈭䉪䊧䊷䉺䊷䈲㛳䈒䈾䈬ᢙ䈏ዋ䈭䈇䇯䈠䈱ઁ䈱䉪䊧䊷䉺䊷ᶖ෰䊜䉦䊆䉵䊛 䈱⸽᜚䈮䈭䉎䈎䉅䈚䉏䈭䈇䇯ᦨㄭ䈱⏕₸⊛ᶖ෰䉟䊔䊮䊃

Შ&KUVTKDWVKQPQHETCVGTUQP+VQMCYCQDUGTXGFD[VJG*C[CDWUC OKUUKQPǤȈǫȯƷǯȬȸǿȸ݅ࡇ䂾⋥ᓘ100 m એ਄䋺㵪䉪䊧䊷䉺䊷↢ᚑ䈫ᶖ෰䈏ᐔⴧ䈭㵰㘻๺㵱⁁ᘒ䂾⋥ᓘ10-100 m 䋺㵪㘻๺એਅ䂾⋥ᓘ~10 m એਅ䋺㵪㗼⪺䈮ዋ䈭䈒䈭䈦䈩䈇䉎Fig.1䋺䉟䊃䉦䊪䈫䉣䊨䉴䈱䉪䊧䊷䉺䊷ኒᐲ䉕R-plot䈮␜䈚䈢䉅䈱㶎䉣䊤䊷䊋䊷䋺N1/2㶎ዊ䈘䈇䉪䊧䊷䉺䊷䈱䈾䈫䉖䈬䈲䉟䊃䉦䊪䈱"smooth terrains"䈮⷗䈧䈎䈦䈩䈇䉎(Hirata et al., 2009)䇯

Შ/QFGNQHETCVGTCEEWOWNCVKQPQP+VQMCYC U UWTHCEG
Შ5ECNKPINCYUHQTETCVGTHQTOCVKQPᆔ᫏ƷǹǱȸȪȳǰЩǛ̅ဇ䊶Strength-A䋺䋨shear flow 䉕⠨ᘦᄖ䋩㵪O‘Brien et al.(2006)䋺䉧䉴䊒䊤䈱䉪䊧䊷䉺䊷ᒻᚑ䉲䊚䊠䊧䊷䉲䊢䊮(Nolan et al., 1996)䈮䈩ᧂ⍮ᢙ䉕᳿䉄䈢㱜䉴䉬䊷䊥䊮䉫
䊶Strength-B䋺 䋨shear flow 䉕⠨ᘦᷣ䋩㵪 Holsapple(1993)䋺㒽਄䈱῜⊒䉪䊧䊷䉺䊷䈮ၮ䈨䈒䉴䉬䊷䊥䊮䉫ೣᲨ/QFGNRTQLGEVKNGRQRWNCVKQPᆔ᫏Ʒᘔᆳ‫˳ټ‬ЎࠋȢȇȫǛ̅ဇ(㶎 NEA䈱䉪䊧䊷䉺䊷䈱䈾䈫䉖䈬䈲䊜䉟䊮䊔䊦䊃䈪૞䉌䉏䈢䉅䈱䈫઒ቯ)

䊶OBGಽᏓ䋺㵪O‘Brien et al.(2006) 䈪ⴣ⓭ಽᏓ䈫䈚䈩૶䉒䉏䈢䊜䉟䊮䊔䊦䊃ಽᏓ
䊶BALಽᏓ䋺
㵪Bottke et al.(2005)䈱䊝䊂䊦䉕૶䈉䈖䈫䈮䉋䉍૞䉌䉏䈢ⴣ⓭ಽᏓ䈖䉏䉌2䈧䈱ಽᏓ䈱䈬䈤䉌䈏䇮䉟䊃䉦䊪䋨෸䈶䉣䊨䉴䋩䈱䉪䊧䊷䉺䊷ಽᏓ䈮ᦨ䉅⦟䈇৻⥌䉕␜䈜䈎⺞䈼䈢䇯Შ%TCVGTGTCUWTGRTQEGUUGUǯȬȸǿȸǛෞƠƯƠǇƏᢅᆉƱƸᲹ䂾㊀䈭䉍ว䉒䈞䋨䉪䊧䊷䉺䊷䈏㘻๺⁁ᘒ䈮ㄭ䈇䈫䈐䋩䊶ዊ䈘䈭䉪䊧䊷䉺䊷䋺㵪ᄢ䈐䈭䉪䊧䊷䉺䊷䉕ᶐ㘩䈚䇮䉉䈦䈒䉍䈫ⷒ䈉䊶ᄢ䈐䈭䉪䊧䊷䉺䊷䋺㵪䈠䉏䈏ᒻᚑ䈘䉏䉎႐ᚲ䈪䈜䈼䈩䈱䉪䊧䊷䉺䊷䉕ᶖ䈜䂾࿾㔡േ䊶ዪᚲ⊛䈭࿾㔡േ䋺㵪ᄢ䈐䈇䉪䊧䊷䉺䊷䈱䈜䈓ㄭ䈒䈱䈫䈖䉐䈮䈅䉎䉪䊧䊷䉺䊷䉕ᶖ䈚ᓧ䉎䇯䊶ዊᖺᤊ䈱ో૕䈱࿾㔡േ䋺㵪ᛂ䈤਄䈕䉌䉏䈢䊧䉯䊥䉴䈪䇮ዊᖺᤊో૕䈱⴫㕙䈱䉪䊧䊷䉺䊷䉕ᶖ䈚ᓧ䉎䇯䊶ᄙ䈒䈱ዊ䈘䈭ⴣ⓭䈱⚥Ⓧ䈱ലᨐ䈮䉋䉎࿾㔡േ䋺㵪ዊ䈘䈭䉪䊧䊷䉺䊷䉕ᶖ䈚ᓧ䉎䇯Შ5GKUOKEUJCMKPIGTCUWTG‫ע‬ᩗѣƴǑǔෞӊƴƭƍƯ
Richardson et al.(2004, 2005)䈲
䉣䊨䉴䈮䈧䈇䈩ⴣ⓭Ფ䈱࿾㔡䈱વ᠞ቯᢙKi䉕⷗Ⓧ䉅䈦䈢䇯䋨Fig.4䋩䂾 4 m 䈪௑䈐䈮ᄌൻ䈏䈅䉎䋺㵪ᢳ㕙䈪䈱䊧䉯䊥䉴䈱േ䈐䈏㵰stick-slip” 䈎䉌 㵰hop-slip” 䈻⒖ⴕ䈚䈢䉟䊃䉦䊪䈱⒖ⴕ
䈲䈬䈖䈎䋿⋥ᓘDa䈱ዊᖺᤊ䈱⴫㕙䈮⥄ಽ䈱
㊀ജടㅦᐲ䈮඘ᢜ䈜䉎ടㅦᐲ䉕ᒁ䈐⿠䈖䈚ᓧ䉎䊒䊨䉳䉢䉪䉺䉟䊦⋥ᓘ Dp
(Richardson et al.(2005) Eq.7)

Dp 㺘 Da5/3
䂾 䉟䊃䉦䊪䋺Dp䋽⚂ 5 mm

Შ&KUEWUUKQPCDQWVUGKUOKEUJCMKPI‫ע‬ᩗƷˡછ‫ܭ‬ૠ-KƷᙸᆢǋǓ䉟䊃䉦䊪䈮䈍䈇䈩䈱Ki䈱௑䈐䈲᳿䉁䈦䈩䉅䇮䊤䉟䊮䉕᳿ቯ䈪䈐䈭䈇䇯䋨㺰 ࿾㔡േ䉕⿠䈖䈘䈭䈇ዊⷙᮨ䈭䊒䊨䉳䉢䉪䉺䉟䊦䈏
5 mm એ਄䈪䈅䉎䈎䉅䈚䉏䈭䈇䈢䉄䋩੹࿁䇮䉟䊃䉦䊪䈮㑐䈚䈩䈱ฦ䇱䈱䊒䊨䉾䊃ਛ䈪䇮ᦨૐ䈱Ki䈱䊤䉟䊮䉕↪䈇䈩ታ㓙䈱䉪䊧䊷䉺䊷ಽᏓ䈮䊐䉞䉾䊃䈘䈞䈢䇯Შ/QFGNKPIVJGETCVGTJKUVQT[QP+VQMCYC CPFEQORCTKUQPYKVJ'TQU$#.Ўࠋ 1$)Ўࠋ  5VTGPIVJ#ưȕǣȃȈ (KI᳸ǤȈǫȯ᳸䊶 BALಽᏓ䋨਄࿑䋩䋺㵪⋥ᓘ10 m એ਄䈱䉪䊧䊷䉺䊷䈪䉋䈒䊐䉞䉾䊃䈜䉎䇯䊶 OBGಽᏓ䋨ਅ࿑䋩䋺
㵪BALಽᏓ䈮䈲䈇䈒䉌䈎ഠ䉎䈏䉋䈒䊐䉞䉾䊃䈚䈩䈇䉎䇯⋥ᓘ10 m એ਄䈱䉪䊧䊷䉺䊷ಽᏓ䉕ౣ⃻䈜䉎䈱䈮ᔅⷐ䈭ᤨ㑆䋽⚂ 75 Myr

$#.Ўࠋ 5VTGPIVJ$ǹǱȸȪȳǰЩưȕǣȃȈ (KI᳸ǤȈǫȯ᳸⋥ᓘ10 m એ਄䈱䉪䊧䊷䉺䊷ಽᏓ䉕ౣ⃻䈜䉎䈱䈮ᔅⷐ䈭ᤨ㑆䋽⚂ 900 Myr

㶎 Strength-A䉋䉍䉅⚂ 䋳 ୚ዊ䈘䈭⋥ᓘ䉕੍᷹䈚䈩䈇䉎䋫䉰䉟䉵ಽᏓ䈱௑䈐䈏⚂ 2.7䈖䉏䈲Strength-A䈱䈫䈐䈱䉪䊧䊷䉺䊷ᐕ㦂䈱⷗Ⓧ䉅䉍䈫䈙䈦䈒䉍10䈱䊐䉜䉪䉺䊷䈱㆑䈇䈮䈭䉎䇯
㶎 3 2.7 㻍19

$#.Ўࠋ  5VTGPIVJ#$ ưȕǣȃȈ (KI᳸Ǩȭǹ᳸䊶 Strength-A䋨਄࿑䋩䋺䉪䊧䊷䉺䊷ಽᏓ䉕ౣ⃻䈜䉎䈱䈮ᔅⷐ䈭ᤨ㑆
䋽~100-200 Myr
䊶 Strength-B 䋨ਅ࿑䋩䋺䉪䊧䊷䉺䊷ಽᏓ䉕ౣ⃻䈜䉎䈱䈮ᔅⷐ䈭ᤨ㑆
䋽~1000-2000 Myr

Შ6JGQTKIKPQHVJGFGHKEKGPE[QHVJG
UOCNNGUVETCVGTUQP+VQMCYC
ǤȈǫȯƷႺࢲOˌɦƷǯȬȸǿȸƸီಮƴ‫ݲ‬Ƴƍ᳸ƦƷྸဌǛਖ਼ยí᳸
䂾 NEA䈲䇮䊜䉟䊮䊔䊦䊃ዊᖺᤊ䈫Ყ䈼䈩㆝䈎䈮ዋ䈭䈇䈖䈫䉟䊃䉦䊪䈲ర䈲䊜䉟䊮䊔䊦䊃ਛ䈮䈅䉍䇮䈠䈖䈪ᄙᢙ䈱䉪䊧䊷䉺䊷䉕ᒻᚑ䈚䈩䈇䈢䇯⋥ᓘ10 m એਅ䈱䉪䊧䊷䉺䊷䉕ᶖ෰䈪䈐䉎ᄢ䈐䈭ⴣ⓭䈏䈅䈦䈢䈫䈜䉎䈫㵪䇮㵪䈠䈱ⴣ⓭䈲䇮䉟䊃䉦䊪䉕䊜䉟䊮䊔䊦䊃䈱ᄖ䈻಴䈚ᓧ䉎䇯㹢 䈠䉏એᓟ䈱䉟䊮䊌䉪䉺䊷䈲ᢙ䈏ዋ䈭䈇ઁ䈱NEA䈱䉂䈪䈅䉎䇯ǤȈǫȯƷႺࢲOˌɦƷǯȬȸǿȸƸီಮƴ‫ݲ‬Ƴƍ᳸ƦƷྸဌǛਖ਼ยî᳸䂾 䉟䊃䉦䊪⴫㕙䈱䈾䈫䉖䈬䈲ᄢ䈐䈇ጤ䈪䈑䈦䈚䉍ⷒ䉒䉏䈩䈍䉍䇮
䈠䉏䈏"㎸"䈱䉋䈉䈮ᝄ䉎⥰䈦䈩䈇䉎䈖䈫ዊ䈘䈇䉪䊧䊷䉺䊷䉕ᒻᚑ䈜䉎䈲䈝䈱ዊ䈘䈇䉟䊮䊌䉪䉺䊷䈏䇮ጤ䉕⎈䈒䈱䈮૶䉒䉏䈩䈚䉁䈦䈩䈇䉎䇯䋨䈖䈱⷗⸃䈲䉟䊃䉦䊪䈱"smooth terrains"਄䈪ዊ䈘䈭䉪䊧䊷䉺䊷䈱䈾䈫䉖䈬䈏⷗䈧䈔䈩䈇䉎䈫䈇䈉᷹ⷰ䈮⍦⋫䈚䈭䈇䋩ǤȈǫȯƷႺࢲOˌɦƷǯȬȸǿȸƸီಮƴ‫ݲ‬Ƴƍ᳸ƦƷྸဌǛਖ਼ยï᳸䂾 Ყセ⊛ᦨㄭ䈮ೋᦼൻ䉟䊔䊮䊃䈏䈅䈦䈢䈎䉅䈚䉏䈭䈇䈖䈫~100 Myr 䋨Strength-A䋩䈅䉎䈇䈲~1000 Myr 䋨Strength-B䋩䉟䊮䊌䉪䉺䊷䈱῜᠄䈮ᤴ䈘䉏䈢ᓟ䇮⋥ᓘ~10 m એਅ䈱ో䈩䈱䉪䊧䊷䉺䊷䉕ᶖ䈜䈏䇮⋥ᓘᢙ~10 m䈱ᄢ䈐䈭䉪䊧䊷䉺䊷䈲⛽ᜬ䈜䉎䈅䉎⒟ᐲᦨㄭ䈱ೋᦼൻ䉟䊔䊮䊃䈏䈅䈦䈢䇮䈫䈇䈉䉅䈱䇯⃻࿷䈱ዊ䈘䈇䉪䊧䊷䉺䊷ಽᏓ䈲䇮䈠䈱ೋᦼൻ䉟䊔䊮䊃એᓟ಴᧪䈢䉅䈱䈪䈲䈭䈇䈎䇯
䋨1000 yr ೨ᓟ䋨Strength-A䋩 䇮10000 yr ೨ᓟ䋨Strength-B䋩 䋩䇯έƷਖ਼ยï И஖҄ǤșȳȈ Ʒദࣱ࢘Ʊφ˳ႎƳʙᝋ
䂾 Scheeres et al.(2007)䊶᭴ᚑⷐ⚛ౣ㈩⟎䋺㵪䉟䊃䉦䊪䈲䈖䈖10ਁᐕએᤄ䈮ᦨ䉅ㅦ䈒࿁ォ䈚䈩䈇䈢䉋䈉䈪䈅䉍䇮YORPലᨐ䈮䉋䉍䇮⃻࿷䈱࿁ォ₸䉁䈪ᷫㅦ䈚䈢䇯࿁ォㅦᐲ䈱ᄌൻ䈮઻䈉ᄌᒻ䈪䇮⃻࿷䈱ਥⷐ䈭᭴ᚑⷐ⚛
䈻ౣ㈩⟎䈚䈢䇯䋨10-100 kyr ⷐ䈜䉎䋩
䂾 Fujiwara et al.(2006)䊶ᄢ䈐䈭ⴣ⓭䋺㵪䉟䊃䉦䊪䈱૕(body)䈱ㇱಽ䈏䉅䈫䉅䈫න૕‛䈫䈚䈩ሽ࿷䈚䈩䈍䉍䇮ᄢ䈐䈭ⴣ⓭䈏⃻࿷㚂䈱ㇱಽ䈪⷗䉌䉏䉎䈒䈶䉏䈢ㇱಽ䉕ᒻᚑ䈚䈢䇯Შ%QPENWUKQPU䊶䉟䊃䉦䊪⴫㕙䈱䉪䊧䊷䉺䊷ผ䉕⸘▚䈜䉎䈢䉄O‘Brien et al.(2006)䈱䊝
䊂䊦䉕૶䈉䈖䈫䈮䉋䈦䈩䇮䉪䊧䊷䉺䊷䉰䉟䉵ಽᏓ䉕ౣ⃻䈚䈢䇯䊶䉟䊃䉦䊪䈱䉪䊧䊷䉺䊷⚥Ⓧ䈮ᔅⷐ䈭ᤨ㑆䈏~75 Myr 䈎䉌1 Gyr 䈪䈅䉎䇯䊶䉟䊃䉦䊪䈱ዊ䈘䈇䉪䊧䊷䉺䊷䋨 < 10 m 䋩䈱ᰳਲ䈲䇮੹࿁૶䈦䈢࿾㔡േ䈱ᐔⴧ䊝䊂䊦䈮䉋䈦䈩✊㤀䈮⺑᣿䈜䉎䈖䈫䈲䈪䈐䈭䈇䇯䊶䈚䈎䈚䇮․ቯ䈱䉟䊔䊮䊃㵪଀䈋䈳䇮 Scheeres et al.(2007)䈮䉋䈦䈩ឭ᩺䈘䉏䈢䇮㗡䈫૕䈏䈒䈦ઃ䈇䈢䈫䈇䈉ૐㅦᐲⴣ⓭㵪䈲䇮ዊ䈘䈭䉪䊧䊷䉺䊷䈱ᶖ෰䈮䈧䈭䈏䉎䈎䉅䈚䉏䈭䈇䇯䊶䈠䈚䈩䈠䉏䈲䉟䊃䉦䊪਄䈱䉪䊧䊷䉺䊷ಽᏓ䈫੹࿁䈱䊝䊂䊦䈱੍᷹䈫䈱㘩䈇㆑䈇䋨ዊ䈘䈭䉪䊧䊷䉺䊷䈏ዋ䈭䈇䈖䈫䋩䉕⺑᣿䈜䉎䈎䉅䈚䉏䈭䈇䇯